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Category : Physics


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QAId : 2727024
Asker : priyaimports@...
Subject : little doubt
Private : No

Question : thank u sir but i have doubt.you said that momentum is what makes things harder to stop .is it a force.for eg: we can take two cars A and B go in same direction IN THIS WERE IS THE MOMENTUM.WHEN A COLLIDES WITH B IS IT THE
MOMENTUM.TO PROVE IS THERE ANY EXPERIMENT

Answer : If A and B are travelling in the same direction how ill they collide? :-)

Their momentum is expressed as the effort it will take to bring them to rest. So a car travelling alone (without hitting anything) has momentum by virtue of the fact it will take X amount of force expenditure to bring it to a halt. Another word for this resistance to stopping is called impetus.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5


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QAId : 2730874
Asker : jhala1313
Subject : help
Private : No

Question : hi,
An amusement park ride features a small electric replica of the ThrustSSC car running on a straight, 600 foot, track. The car always moves with constant acceleration, positive or negative.
You have two controls: A and D. A causes the car to accelerate with constant acceleration, D causes the car to decelerate with constant deceleration. The magnitude of the acceleration is twice the magnitude of the deceleration. There are markings on the side of the track in 1 ft intervals.
To start the car you press control A. How far along the track should you travel before pressing control D so that car will stop exactly at the end of the track?

Roger






Answer : I'm going to say you'll need to apply the D (eceleration) button at the 200 foot mark so it will be applied for twice as long a distance as the acceleration button was depressed (since it decelerates at half the rate the A button accelerates at).

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 4


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QAId : 2736909
Asker : raptor660123
Subject : torque
Private : Yes

Question : Yeah I want to know how to measure ft.lb of torque, For example I know that a one foot pole with one pound of down force on the other end will be 1 ft.lb of torque at this end (longer pole more torque). But I want to know what 1 ft.lb of torque is equivalent to in normal pounds ?

Answer : Open this URL:

http://www.unc.edu/~rowlett/units/dictP.html

Press CTRL-F and type torque - it has definitions for all types of units.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

End :


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QAId : 2762921
Asker : ruko
Subject : Jet boat propulsion/airplane wings
Private : No

Question : Dear Sir

Two questions sir:

1) For the benifit of a friend of mine please explain why jet boat exhaust is above the water surface rather than below it.

2) An airplane wing has a certain shape that allows air to flow faster over the top than on the bottom of it. This creats a lower pressure on top which allows the pressure under the wing to create lift. It is called the Bernoli affect (pardon the spelling). This is what is taught in most text books. If this is the only reason why airplanes can fly, how do airplanes fly upside down?

Thank you.

Ruko


Answer : #1 I would expect it's because jets (ala jet airplanes) operate on a principle of instake of air and exhaust of same at higher velocities. IOW - it's not a "water" jet, it's an air jet engine being strapped onto a boat.

#2 - The majority of lift is *not* generated by the Bernoulli effect - it is generated by the forward speed of the plane and the angle of the wing. The faster the plane travels the more air molecules strike the underside of the wing since it is angled upwards. As to why a plane can fly upside down - the Bernoulli effect and the main lift generated by the air striking the underside of the wing are not based on orientation - they are based on forward speed. So it doesn't matter whether the plane is upside down or sideways - the lift is still generated. All other directions of travel (as in to not have "lift" towards the ground which is what you were implying I think) are still a function of the control surfaces of the plane (tail rudder, ailerons, flaps).

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

FUQuestion : Dear Sir

Jet boat propulsion:

I am referring to the "personal water crafts" like Yamaha, Skidoo etc. The ones that are driving people nuts on lakes and rivers. They have a pump which forces a "jet" of water out the back driving the boat forward. The exhaust or jet is above the water and I was wondering why it would not be below the water surface.

Thanks

Ruko

Answer : Oh... well for those I'd expect it's because the engine burns gasoline and air (oxygen). And because if the exhaust *were* placed underwater (to somehow get some extra "boost" if that's what he means by this question) there is a threat (when not under full throttle) of getting water back up *into* the engine which is a Bad Thing (tm).

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

FUQuestion : Paul

Thank you for your response.

The "exhaust" I'm talking about is not engine exhaust. I am sorry I used the word exhaust, it probably does not fit here. I am talking about the jet of water out of the nozzel in back that drives the little annoying boats forward. It is above the water surface. My question is why is it above the surface rather than below it?

Thanks

Ruko

Answer : Are you referring to this stream that is ejected from the back-top of the waverunner?:

http://www.yamaha-motor.com/01watercraft/01wcimages/500/01XL12_ACTION_L_500.jpg

If so, I'd suggest it is simply a pressure-relieving mechanism and the primary output of the "jet" is indeed submersed. It probably helps avoid undue pressure build-up in the engine/jet area due to water pressure fluctutations.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Answer : Don't forget to rate the answers you receive on AskMe.com...

Rating : 4


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QAId : 2783937
Asker : ronaldsharko@...
Subject : physics, volume of a brick
Private : No

Question : freshman physics. How do I find the weight and volume of 1/2 brick?

Answer : I assume you can get the weight easily with a scale.

The volume is easy to obtain too... Simply fill a jug, or other device large enough to hold the entire brick, with water to the very top, placing this whole device inside another (like a ice tea pitcher filled with water sitting inside a tupperware rectangular bin). Now simply (slowly) introduce the brick into the water-filled pitcher (being sure not to put your fingers or hands into the water too). The water that gets displaced is equal to the volume of the object that displaced it. So all you have to now is pour the water that was displaced (and captured) into the tupperware and pour it into a measuring cup marked with measurements and you will have the volume of an irregular object such as this brick.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5

Answer : You can find the mass by using a balance (scale with two sides, a pan on each side, suspended by a frame). This differs from a normal "weighing" scale, in that it does not measure the force of gravity on the object (it's "weight"), but rather to bring the balance into equilibrium, an *equivalent mass* must be placed on the opposite side balance pan. This means that you can use the little metric weights (masses) with handles on them that come in 1gm, 1mg, etc sizes to balance the brick and find it's mass. This works where a scale does not because it is independent of any other factors. You can successfully find the mass of the brick as easily on Earth as on the surface of the moon, even though the moon's gravitational pull (nad the resultant wight produced) are only 1/6 that of Earth.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



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QAId : 2785576
Asker : rfeinberg61
Subject : what is a coulomb
Private : No

Question : I am taking a basic electronics course. The definition given of a coulomb is the charge possessed by 6.25 x 10 (to the power of 18) electrons. Where did that number come from? If it was an arbitrary number set as as standard, why that number.

Answer : For electrically-charged objects this amount just happened to turn out to be a constant of attraction/repulsion (since the charges can be considered to be unchanging, the only other changing factor between comparing repulsion/attraction was distance).

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

FUQuestion : I now understand that the number 6.25x10^18 is a constant. But could you clarify what is meant by a constant of attraction/repulsion?

Answer : The electrical repulsion/attraction force, when measured, was found to fit the following formula:

F = k * (q1 * q2)/d^2

F is the force of attraction/repulsion
k is the constant (later defined as a coulomb)
q1 and q2 are the charges themselves
d is the distance between the charged particles (being squared here)

The formula was made to fit our experience of the world as we found it, not the other way around. Charles Coulomb happened to find that when the other elements of the equation are put in with this contant value the force could be predicted. So the value got a name (coulomb) and we got a formula that fits our reality and allows us to make some more predictions. That's how these things work - not always a tidy explanation, but an item that is useful in describing and working with the things we know/explore.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5


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QAId : 2788099
Asker : bijuo
Subject : blackholes
Private : No

Question : what is a black hole and do you know anything about time-space continum?

Answer : A black hole is a collapsed star I believe... it has surpassed the mass required for it to generate a gravitational field so strong that light can no longer escape from it's immediate vicinity (which is why it appears as an empty space).

Time-space continuum? I think that is an acknowledgement that you can't discuss time without involving the concept of space, since all of our concepts of time involve motion (Earth around the sun, etc).

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



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QAId : 2812411
Asker : elisehague
Subject : efficiency of a golf ball
Private : Yes

Question : How does the surface effect the way a golf ball bounces?(does it have anything to do with friction?)
Also, how does the temperature of a golf ball effect the way it bounces?
Thanks

Answer : I don't think that a golf ball's bounce or roll is significantly affected by the "dimpling" on the ball surface. Spin of the ball when it lands and velocity (includes direction as well as speed of travel) are the primary factors. The dimpling does help to generate lift while the ball is in flight. Depending on the spin imparted to the ball the ball can climb, drop faster, or veer left or right (as anyone who has shot them into the woods can testify :-).

I would say that the warmer the ball the higher it will bounce. Since the core is rubber and rubber becomes less flexible the colder it gets (and more the earmer it gets) it stands to reason it will bounce higher when warm. Try putting a rubber "superball" into a freezer for a few hours and examine it's lost elasticity when bounced for an extreme example.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities


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QAId : 2839487
Asker : ronaldsharko@...
Subject : PHYSICS
Private : No

Question : THANKS FOR YOUR HELP. HOW DO I CONVERT 500 MILLALITERS TO CENTIMETERS.

Answer : 500 millimeters ("milli" meaning 1000 - 1000mm = 1 meter)

is equivalent to 1/2 of a meter's worth of centimeters. Since there are 100 centimeters in a meter ("cent") then this would be:

50 centimeters

So 500mm = 50cm

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://mem`bers.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5


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QAId : 2863211
Asker : michaelg21386
Subject : The Dangers of Electricity
Private : No

Question : Why is electricity dangerous to humans? Is high voltage and low current or high current and low voltage more dangerous and why?

Hope you can help, Michael

Answer : Electricity can interfere with the nervous system. Plus it causes severe muscle contractions, and if there is enough current can cause severe burns.

Both voltage and current are dangerous.

Voltage is what gets the electricity into you; current is what kills you.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 3


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QAId : 2953953
Asker : WWJONES35
Subject : Video & Audio Tapes about Physics
Private : No

Question : I enjoy the video & audio tapes written by Stephen Hawkins " A Brief History of Time & Universe." They are presented in a clear, understandable, concise manner- not redundant, superfluous or self-serving.
Conversely, I recieved as a gift, some audio tapes entitled "The Great Courses on Tape, Einstein's Relativity and the Quantun Revolution: Modern Physics for Non-Scientist Part I and Part II," put out by "The Teaching Company" of Springfield, VA, which I rate as D+!!!

Do you know of a source for Video and Audio Tapes of General Science and/or Physics?

Answer : I found many by going to amazon.com and performing a search (in Books) for

audio physics

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 2


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QAId : 2971084
Asker : Anonymous
Subject : speed of light
Private : No

Question : What is 4.7 times faster than the speed of light?

Answer : A serious speeding ticket that will lose you your license...

No seriously... this sounds like a trick question but I'll answer it anyway.

4.7 x 186,282 = 875,525.4 miles per second.

This number 4.7 seems familiar... are you leading up to some kind of speed insinuation for an original IBM PC (X86 running at 4.77 Mhz)? hehe

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



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QAId : 2973210
Asker : lilstinkis
Subject : ELECTROMAGNETIC PESTICIDES
Private : Yes

Question : HELLO~
I'M GLAD THAT I SAW YOUR NAME. YOU SEEM TO KNOW MUCH ABOUT THE ELECTROMAGNET SUBJECT. PLEASE HELP ME FIND THIS ANSWER. MY FIANCE AND I ARE MOVING TO MD IN ABOUT 2 1/2 WEEKS AND I MUST STAY WITH MY SISTER IN LAW FOR 4 WKS WHILE OUR HOUSE IS BEING CONSTRUCTED. SHE USES THAT PESTICIDE CALLED RIDDEX PLUG IN ELECTRONIC UNIT. I CANNOT SEEM TO BE ABLE TO TALK HER INTO UNPLUGGING THE UNIT WHILE WE STAY WITH HER. I OWN 2 FERRETS, A GUINNEA PIG, AND A CAT. I HAVE ALSO HAD 2 BRAIN SURGERIES AND 8 CEREBRAL HEMORRAGES. I AM SO CONCERNED ABOUT THE ELECTROMAGNETIC PULSES BOTH HARMING MY ANIMALS AND MYSELF. PLEASE HELP!!! (BY THE WAY QVC SEEMS TO BE THE ONLY PLACE THAT EVEN CARRIES THIS UNIT. ONE IS NEEDED ON EACH FLOOR TO REMAIN AFFECTIVE. WE WILL BE STAYING IN A 90% CONCRETE UNFINISHED BASEMENT)

Answer : I am not familiar with this unit but just upon inspection of the QVC non-technical description it appears that at the very least your guinea pig and perhaps the ferrets will not be able to tolerate the fields given off by these devices.

http://www.qvc.com/asp/frameset.asp?nest=%2Fasp%2FIsItemNumberRedirect.asp&search=SQ&frames=y&referrer=QVC&txtDesc=riddex

I would suggest that you ask her nicely once again and if she will not (amazing considering your history of problems - if I even suspected it *might* have an effect on you I would remove it without question!) then I'd suggest you make other plans for a place to stay for those 4 weeks. Ask her how she might feel were you to have a stroke due to her refusal? A treatment of a traditional insecticide could easily take the place of these devices for the month you'll be there.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5


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QAId : 2993306
Asker : priyaimports@...
Subject : momentum
Private : No

Question : dear sir

in same topc i have a doubt .let us consider
two bodies coming with same velocity with same
mass .if you stop the body before it collidesit momentum will be high due to high velocity.but after it collides it momentum will be less because it velocity will reduce .then who can they say .momentum after impact = before impact

Answer : You can say there was momentum before impact because you now see the results of the needed forces to bring those objects to a halt - namely, both are now *not* moving and if objects such as cars were involved you see the force required to bring them to rest in the form of smashed cars. I'm really not sure where you're confused.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

FUQuestion : THAK YOU SIR I UNDERSTOOD IT. NOW WE CAN TAKE THE TOPIC .CURRENT , IN TELEVISION WHAT WHO CURRENT ENERGY IS CONVERTED TO VISION. IS CONVERTED IN TO WHAT.WHAT IS PRESSURE.
THEY SAY ATOMIS A SMALLEST PARTICAL.PROTONS
,ELECTRONS AND NEWTRONS ARE REVOLVING ARROUND THE ATOM WHO DO THEY SAY WITH WHAT REASONS WHAT IS CURRENT AND WHAT INSIDE IT OF WHAT T IS MADE I WHAT TO DETAILE STUDY ABOUT CURRENT

Answer : That question is hard to read, but I think I got parts of it.

A TV works by shooting a scanning beam of electrons to the inside surface of the TV tube (which is coated inside with phosphors). The phosphors on the inside of the TV are excited and emit light of an intensity based on the excitation levels given it. The different colors come from combining each "element" on the screen into what are called "triads". These triads consist of a red, green and blue element, all three together making one visible item on the screen.

As for atoms being the smallest units I believe the "quarks" have that distinction at the moment. They are building blocks of the atomic parts (electrons, protons, and neutrons). As for the orbits the electrons "orbit" (actually "exist at a particular place inside an orbit shell whenever they please" is a more accurate statement) a nucleus that is composed of protons and neutrons.

Current is simply the flow of electricity measured in units of time.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Answer : Don't forget to rate the answers you receive on AskMe.com...

FUQuestion : in every particals ther is atom in the atom theris nucleuse and in the nucleuse ther are protons and neutrons .they are positive and nagative charge.what do you mean positiveand negative charge.what is a charge.beam of electrons.who do they say that the protons and electrons revolve around the neucleus .what to no reason behind every thing

Answer : Protons are positive in charge. Neutrons have no charge. Electrons are negative in charge and "orbit" the nucleus.

--
Paul Doherty
http://members.home.net/iqueue



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QAId : 3040633
Asker : demund_98
Subject : cycling
Private : No

Question : I would like to know all physics involved wehn i am cycling an exercise bike such as energy transformation, torque (crank/pedal etc) involved when I pedal, inertia of the wheel, how did the bike get my RPM etc. I would hope that you can be as detail as possible and covers anything that has got to do with physics. Thank You

Answer : Torque is calculated rather simply - assuming you attack the pedal at a perpendicular (most of the time that is true) the torque you produce is simply the force you apply times the distance from the pedal to the fulcrum (in this case the point where the pedal terminates into the crank) minus and retarding forces. As for energy trasnformation there is of course chemical to mechanical energy transformation in you as you convert that cheeseburger into muscle movement. ;-) Inertia of the wheel would apply mainly on the initial startup of the wheel. Once it's moving it is easier to keep moving (rolling friction it's called). Rotational inertia of the wheel then steps in, but it has more to do with keeping the wheel pointed straight ahead (resisting sideways torques). This is part of what keeps bicycles easily controllable at speed (and keeps you from falling over). The bike gets the RPM probably from having a sensor on the frame that can tell when a part of the tire/wheel passes by it. Then it simply counts how often that part passes by over a given period of time and that gives the RPM. So say you are pedalling hard and the sensor sees the "flag" pass by 10 times in 10 seconds. Then the RPM would be calculated (for that instant) as 60 RPM since if that rate were maintained you would do 60 flag passes in 60 seconds.


More info on the physics of cycling can be had in these two other answers I've previously given...

http://www1.askme.com/SearchResults.asp?pm=va&cid=852&xShowNew=1&QA=on&AnswerRating=1&xid=50373&query=bike&prev=QA%2520&vid=2575374

http://www1.askme.com/SearchResults.asp?pm=va&cid=852&xShowNew=1&QA=on&AnswerRating=1&xid=50373&query=bicycle&prev=QA%2520&vid=907080

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5


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QAId : 3044361
Asker : mbishop@...
Subject : physics
Private : No

Question : How long does it take light to travel from the sun to the earth?

Answer : About 8 minutes...

Here is a table of distances and times for the planets:

http://sohowww.nascom.nasa.gov/explore/faq/astronomy.html#LIGHT_TIME_TO_PLANETS

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



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QAId : 3086744
Asker : ph_aser
Subject : vision
Private : No

Question : If in subtractive colour (i.e. mixing of paints) the resulting colour is determined by the overall reflective properties of the paints involved, then how come black isn't the result of a mixture of two or more different colours?

For example if red paint reflects red light and absorbs the other frequencies of light and yellow reflects only yellow and absorbs the others, then surely when the two are mixed the red pigment will absorb yellow light and the yellow will absorb red resulting in no light being reflected. Can you explain why this is not so?

Answer : It is not so because you have mistakenly identified red as a primary subtractive color when it is not. Red is a primary *additive* color. The three primaries for subtractive coloring (as in a printing press) are:

yellow
cyan
magenta

Where each overlaps another a color is produced by the mechanism you described. For example:

When yellow and cyan overlap the resultant (left over) color is green. When magenta and yellow are used the result is red. Only when white light passes through all three of these subtractives are all frequencies removed for a result of black.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities





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QAId : 3087861
Asker : tony92
Subject : ANSI Lumens
Private : No

Question : What is the formula for converting footcandle to ANSI Lumens?
I have a Illuminometer but it does not indicate lumens on the meter display.


tony@avpres.org

Answer : This site has a good discussion on it:

http://www.a1.nl/phomepag/markerink/lumencan.htm

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



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QAId : 3099646
Asker : poorpg
Subject : Time , 24 hours?
Private : No

Question : Why there is 24hrs a day, but not ten instead?

Answer : Cecil Adams has already answered this one better than I... (the following taken from http://www.straightdope.com/classics/a1_125.html):

Dear Cecil:

My question arises from the fact that my kitchen happens to have both a boldly appointed digital clock and an old noisy analog thing my grandmother bought around 1940. I was delighted to discover quite by accident one bloodshot night that I could read the time on granny's clock from a far greater distance, and with much less light, than I could its digital counterpart. However, it occurred to me that were it to have been divided into eight equal sections, like a compass, reading it would be even less ambiguous. There is an obvious length to our day, but pray tell where is it written that it have 24 divisions called hours? --P.P., Chicago

Dear P.:

Well, I could always find it in the back of the Growth in Arithmetic book, along with 16-1/2 feet to the rod. But maybe you had the abridged edition. In any case, we have the Babylonians to thank for our present system of timekeeping.

The number 12 held mystical significance for the ancients, owing to the fact that there were generally 12 full moons a year, and so they divided day and night into 12 parts each. The number 60, apart from being a multiple of 12, is evenly divisible by more integers than any lesser number, and thus was useful for dividing hours into minutes and seconds without the distraction of fractions.

The Babylonian calendar had 12 months of 30 days; since this left five days unaccounted for each year, every sixth year they repeated the month of Adar. The Romans, of course, introduced the present cockeyed system of 28-, 30-, and 31-day months.

While the Babylo-Roman method has a certain primitive charm, it does not make for ease of calculation, and there have been several attempts over the years to devise a more rational system. Perhaps the most famous of these was the social experiment conducted during the French Revolution.

In 1793, in an effort to sweep away the superstitious associations of the old method of timekeeping (you know how revolutionaries are), the French National Convention established a new calendar with 12 months of 30 days each, followed by five (six in leap years) "complementary days," which belonged to no month. Each month was divided into three 10-day "decades," and each day into two sections of 10 hours each. The hour was further divided into 100 "decimal minutes," which were in turn divided into 100 "decimal seconds."

The year began on the autumnal equinox, which happened to be the anniversary of the foundation of the Republic. Each month was given a descriptive name, e.g., Thermidor, July 19-August 17, "month of heat." Each day was also given its own name, some of which were less inspired than others, e.g., Eggplant, Manure, Shovel, Gypsum, Billy Goat, Spinach, and Tunny Fish. Even the French couldn't seriously have felt these represented a significant advance over old faves like Maundy Thursday. Also, on a more practical front, who wants to work a ten-day week?

Nontheless the French public made a valiant effort to implement the new system, going so far as to manufacture watches with concentric 10- and 12-hour dials. But ultimately the task proved to be beyond them. In 1806, after 13 baffling years of missed dentist appointments and overdue library books, they abandoned the revolutionary calendar. This was the only known defeat of Progress in the modern era prior to the establishment of the Illinois General Assembly. Gives you pause, when you think about it.

--CECIL ADAMS



--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5


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QAId : 3135340
Asker : Dave_Va_1999
Subject : windows2000,NT, and win 98
Private : No

Question : Hello
I have a Dell 633 MHZ computer with 20 GB hard drive and 128MB RAM. I have made 3 partitions on the hard drive(2GB FAT 16, 8 GB NTFS, and 8GB NTFS). I have WIN98 on the first partion and now I want to install NT workstation 4.0 on the second partion and Windows 2000 on the 3ed partition, is this possible? I tried it several times, but if I get NT to work windows 2000 doesn't work and if i get windows 2000 to work NT doesn't work. Is it possible to install all these 3 operating systems in one machine? if it is can you please tell me how?
Thanks
p.s: I installed service pack 5 on NT workstation.

Answer : Here is a site with blow-by-blows for installing Windows 2K in tandem with other MS operating systems...

http://www.winmag.com/windows/guides/win2000/

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 2


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QAId : 3143789
Asker : ssheena
Subject : magnetic elevatation
Private : No

Question : whats is magnetic elevatation? it has some priciples to do with electric trains and roller coasters. but how does it work and what is it?

Answer : It's really a simple concept. Try playing with some bar magnets (or just remember when you have done so previously). Each magnet has a north and south pole. Opposite poles (like the north on one magnet to the south on the other) attract each other. Like poles (south to south, for instance) repel. This is the essense of a "maglev" train as they are called as the repulsive magnetic force is used to elevate the train above the track. This makes for very fast trains (some over 300MPH) that have near to no friction or noise generated (plus no pollution to speak of, other than that used to generate the admittedly large amount of electricity such trains consume)). See this page for information and images on these maglev trains:


http://www.abcnews.go.com/sections/tech/DailyNews/maglev990624.html

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



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QAId : 3149760
Asker : Dave_Va_1999
Subject : Win98,NT, and Win 2000
Private : No

Question : pauldoherty gave this response on 9/20/2000:
Here is a site with blow-by-blows for installing Windows 2K in tandem with other MS operating systems...
http://www.winmag.com/windows/guides/win2000/
Hello again
Thanks for the tip.
I went to that site and couldn't find a stright answer to my question. Is it possible to install Win98, NT 4.0, and Win 2000 all in one machine.
thanks again.




Answer : Yes it should work fine...

Install in this order:

98
NT
Win 2K (install to separate partition with "new install" option)

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities




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QAId : 3181167
Asker : penney_4
Subject : electrons
Private : No

Question : Where did electron get its name?

Answer : Here's some info on the electron:

http://encarta.msn.com/find/Concise.asp?z=1&pg=2&ti=761558264

1856 - Physicist Sir Joseph J. Thomson is born in Cheethan Hill, England. He discovered the electron in 1897, and received the 1907 Nobel Prize for Physics.

--
Paul Doherty
http://members.home.net/iqueue


Rating : 3


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QAId : 3181718
Asker : aljufri2
Subject : question
Private : No

Question : what is cold fusion ?
is it myth or reality?
what is the chemistry point of view about it ?
what is the physics point of view about it?
if we comporsion between them can we answer this question "what would be the other sources of energy,I mean"Oil versus what???"

Answer : Cold fusion is the idea of getting light elements like hydrogen to combine to form heavier elements that have a lower mass-per-nucleon. A small percent of the mass differential is converted to energy.

The problem with fusion is that when you try to fuse nuclei together the only items inside the nucleus with a charge are protons. Protons have a positive charge and *repel* other protons. So to get two nucleuses to bond means you have to overcome that resistance. Usually to do this requires a great amount of heat to get the atoms moving at a very high rate of speed. Only with these tremendous speeds can the repulsive force be overcome.

Cold fusion is an attempt to produce this effect by chemical means. Unless someone is exceptionally clever at it I'm not sure it's all that viable of a concept. Only time will tell.

Competing forms of power generation are nuclear fission, coal, natural gas, hydroelectric, thermic, solar, wind... I may be missing a few but that's probably all the big ones.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5


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QAId : 3220253
Asker : Friiends
Subject : Hi!!!!!!
Private : No

Question : can u tell me a little information on wat anti-matter is?
thanks a lot, Asheigh

Answer : Here is Cecil's answer on the subject (always good for info and a laugh)...

http://www.straightdope.com/mailbag/mantimatter.html

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities





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QAId : 3232024
Asker : ata6x
Subject : Physics, Biology, and Projectile Motion
Private : No

Question : There is a field that links biology and physics and also uses projectile motion. What is it?

Answer : It's called NASA (space exploration)... ;-)

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5


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QAId : 3239956
Asker : emarlo
Subject : Physics Question
Private : No

Question : I am a student at BU in an Elementary physics class. I have one problem that I can't seem to get an answer to. The problems reads as follows:

At serve, a tennis player aims to hit the ball horizontally. What minimum speed is required for the ball to clear the .90m high net about 15.0m from the server if the ball is "launched" from a height of 2.50m? Where will the ball land if it just clears the net (and will it be "good" in the sense that it lands within 7.0m of the net)? How long will it be in the air?

I would greatly appreciate your help on this problem

Thanks,
emarlo

Answer : OK, here we go.

distance from server to net - 15m
height of net - .9m
height of ball at horizontal launch - 2.5m
maximum distance travelled for "good" shot - 22m (15m + 7m on other side of net)

The first thing we need to find is how far the ball can fall before it will not clear the net. It's starting at 2.5m and will not clear after the level of the net, .9m, so we simply subtract .9 from 2.5m and get 1.6 meters. This is the maximum distance we can fall before crossing the net.

So now we need to know how long that fall (1.6m) takes. Since the gravitational acceleration is unaffected by our shot speed we can safely calculate this time by this:

1/2gt^2 = 1.6

(1/2 * g (9.8m/sec))

4.9*t^2 = 1.6

(divide both sides by 4.9)

t^2 = .33

(take the square root of each side)

t = 0.57 seconds to fall 1.6m

Now that we know the time to fall 1.6m we can calculate how fast our ball must travel to cover the 15m from server to net so the ball will cross the net.

0.57 * x = 15m

(divide both sides by .57)

x = 26.32 m/sec

So we must strike the ball at 26.32m/sec speed in order to arrive at the net height in our required time interval of .57 seconds.

Now that we know part of the answer (our minimum shot speed) we can calculate how far the shot will travel at that speed before it hits the ground, and where it will be when it hits. We do this by measuring the time it takes for the full initial ball height (2.5m) to be lost:

1/2gt^2 = 2.5m

(1/2 * g (9.8))

4.9 * t^2 = 2.5m

(divide both sides by 4.9)

t^2 = .51

(take the square root of both sides)

t = .71 seconds

This is the time it will take from launch until the ball hits the ground. Now all we need to do to find the distance travelled is multiply this time by our shot velocity:

.71 * 26.32 = 18.69m

So our ball will travel 18.69m before hitting the ground. The full distance the ball can travel and still be inside the "good" range for a serve is 22m so our shot will be good, and will strike 3.9m away from the net on the other side of the net (18.69m - 15m to net = 3.9 more to travel).

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5
Rating : 5


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QAId : 3290328
Asker : kkwan82
Subject : college studying
Private : No

Question : I just entered college this year and am starting to have problems with my school work already. I would like if you give me some advice on how I should go about studying for my courses.

Physics

I was able to do physics last year in high school (high school physics). As I entered into my physics class just recently in college, I felt that I would be able to do well. However, I just can't seem to handle the quiz and test problems. The professor purposely makes the questions tricky and the wording of the problems are awkward. I'm not sure if I should refer to the textbook. Usually, I don't read the textbook. I just read and do problems in my Schaum's Outline of College Physics review book. However, the review book just doesn't seem to cut it anymore since the problems in the review book are very general and not tricky. I'm not sure what I can do to help myself face physics like this. Can you give me any suggestions or tips?

Thanks very much for your help. I appreciate it greatly.

Kenneth S. Kwan
kkwan82@hotmail.com

Answer : Since I don't know your strengths or weaknesses I would suggest either:

1) Getting a tutor in the subject.

2) Dropping the class this semester and take it at another time from a different professor.

--
Paul Doherty, CNA, CNE, MCP+I, MCSE, A.A.Sc., B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



Rating : 2


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QAId : 3353077
Asker : mothy75
Subject : I swear all are my own questions
Private : No

Question : Dear Pauldoherty,

I promise and swear all questions I asked you are from myself, not any one is copied from any book. If you don't feel comfortable to answer me, it is fine. But I have to clarify again all questions are coming from my thoughts after reading a introduction of a Computer Network book.

Thanks
Tim

Answer : OK... I just tend to avoid those that look like homework. Ask again and I will see if I can help.

--
Paul Doherty
http://members.home.net/iqueue



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QAId : 3428257
Asker : bay37
Subject : static electricity while refueling
Private : No

Question : I know that fires and explosions have occurred while filling portable gas cans sitting in pickup truck beds. Most gas stations now have warnings about how to prevent this. My question: I refill with gas a 26 gallon "Gas Dock" with wheels for marine use. I load it in back of van, fill with gas and slide it down the rear bumper of van. When filled, it is too heavy to lift into van.
Can I safely dissipate any static charge while it is still in the back of the van by connecting a jumper cable to metal valve of "gas dock" and letting the other end of the jumper cable rest on the pavement? I plan to do this before and during the filling operation.
Thank you!

Answer : Cement is not terribly conductive in my understanding, so I wouldn't count on this - plus there is no guarantee that the cement will actually "ground" you (no pun intended... well, ok maybe a little pun intended ;-). If you are curious about this you could hook up an Ohm meter and measure before and after *on an empty gas can* to see if it actually eliminates the juice or not.

I'd do that before I'd be filling that gas can...

--
Paul Doherty
http://members.home.net/iqueue



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QAId : 3455880
Asker : mellanium_mazhar@...
Subject : scalar & vector
Private : No

Question : define equilibrium & its all states.
define centre of gravity & method to find the centre of gravity of irregular shape bodies.

Answer : Equilibrium is a state of balance where forces are counteracted in such a way that accelerations are not taking place.

Center of gravity (also called center of mass) is the central point of the mass of an object. It is considered to be the point that "controls" an objects' state. A basketball for instance has a center of gravity in the center of the hollow space inside, where there is nothing but air. For irregularly-shaped objects (say a strangely-shaped rock) you can find the center of gravity by simply hanging the object from a string *from more than one point* and simply seeing where the vertical lines converge. Draw a line down from the string through the object perfectly vertical towards the ground in both cases - that intersection is the center os gravity.

--
Paul Doherty
http://members.home.net/iqueue



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QAId : 3470532
Asker : bsv3
Subject : Why would seawater below 32 degrees F remain liquid?
Private : No

Question : Why would seawater below 32 degrees F remain liquid?

Answer : Probably because it has so much salt and is not "pure" water.

--
Paul Doherty
http://members.home.net/iqueue



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QAId : 3470557
Asker : xolildorisox
Subject : physics
Private : No

Question : how fast do you have to travel to escape earth's gravity

Answer : A launch speed of 11km/sec is required to escape the Earth's gravitational pull.

A launch speed of 8km/sec is required to orbit an object around the Earth.

--
Paul Doherty
http://members.home.net/iqueue



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QAId : 3477768
Asker : Anonymous
Subject : acceleration of a falling object
Private : Yes

Question : I did an experiment to test the acceleration due to gravity. A paper tape was attached to a machine that held an object of some mass. When the object was released and allowed to fall, the paper tape was marked every 1/40th of a second. I found the distance the object traveled in each interval using a metric ruler. Once I got my data and the results, I calculated the acceleration. It was close to 9.4. The acceleration of a falling object is supposed to be -9.8m/s^2. What could have caused the error in my experiment? Also does the velocity of an object always increase when it’s falling and does the acceleration always stay the same?

Thanks for your help. Please reply soon.

Answer : Was there anything attached to the object that may have impeded it's acceleration (perhaps the apparatus that was marking the tape)? Was the object massive enough that air resistance was negligible?

The velocity of a falling object does continue to increase throughout a fall *until* terminal velocity is reached. TV is the fastest an object can freefall in air. That point is reached when the object is falling fast enough that wind resistance (a function of surface area) is equal to the objects weight. In the absence of air an object would continue to accelerate until it struck the ground. The accelerating force is not entirely uniform as gravitational pull falls off with the inverse-square law so as you approach the Earth the graviational force is greater, and so is your acceleration.


--
Paul Doherty
http://members.home.net/iqueue

Rating : 5


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QAId : 3488135
Asker : emarlo
Subject : Rotor ride
Private : No

Question : This is an interesting problem, but I am having problems figuring it out:

In a "Rotor-ride" at a carnival, people pay money to be rotated in a vertical cylindrically walled "room." If the room radius is 5.0m, and the rotation frequency is .50 revolutions per second when the floor drops out, what is the minimum coefficient of static friction so that the people will not slip down? Is there really an outside force pressing people against the wall? If so, what is the source?

I would appreciate your help greatly.
emarlo.

Answer : I'm not sure how to calculate the friction coefficient.

As for there being a force from outside, no there isn't. The "force" that is holding the people to the sides of the cylinder is their own velocity, in the form of centripetal acceleration. Since the cyclinder is a curved surface it doesn't allow their bodies to travel the direction they'd like to travel (a straight line) so their bodies are constantly undergoing acceleration (acceleration is a change in velocity - which includes both speed and direction of travel). the force of the surface resisting their attempts to pass through it :-) is the force that keeps them from sliding down it's surface.

--
Paul Doherty
http://members.home.net/iqueue
Rating : 4


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QAId : 3491269
Asker : Anonymous
Subject : heat/a/c
Private : No

Question : is there anywhere on the internet that i can get schematics on various a/c and heating units?

Answer : Here's some...

http://www.repairfaq.org/sam/samschem.htm

--
Paul Doherty
http://members.home.net/iqueue



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QAId : 3539145
Asker : hyde_jackel
Subject : FORCE AND MOMENTUM
Private : No

Question : Hi, heres my question....
You are standing on a log and a friend is trying to knock you off. He throws the ball at you. You can catch it, or you can let it bounce off of you.

Which is more likely to topple you, catching the ball or letting it bounce off?


thanks
HJ

Answer : Letting it bounce off you is more likely to dislodge you from the log...

The ball has a certain momentum as it travels towards you (imparted by your friend). When the ball arrives if you catch it the full force of that momentum is imparted to you (by the force required to stop the ball's flight). If instead you allowed the ball to strike you and bounce off the ball has gone from *having momentum in one direction, to now having momentum in the opposite direction, and the only place that new "negative" momentum can have come from is you*. So the effect of letting the ball bounce is that *more* momentum (in the ball's original direction of travel) is imparted to you than if you had simply caught it.


--
Paul Doherty
http://members.home.net/iqueue

Rating : 5


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QAId : 3587047
Asker : thinkwhy
Subject : fate and the quantum
Private : No

Question : Do you have any idea about the relation between the Quantum physics and fate ?...

Answer : Are you questioning whether fate can exist due to the inability to predict? If so I might respectfully suggest that our inability to predict does not preclude that something beyond our ken dictates our course...


--
Paul Doherty
http://members.home.net/iqueue



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QAId : 3626795
Asker : mindak01@...
Subject : the physics of audio speakers
Private : No

Question : I have a report to do on the physics of audio speakers. I looked around and I couldn't find any sites that would tell me. So do you know the forces involved, velocities, properties, laws of motion, and that kinda thing that goes along with audio speakers? Thanks. Melinda

Answer : I don't know of any sites that discuss this, but the main things I think you'll want to think about are:

Newton's Laws (magnet/speaker-coil movement)
wave motion (longitudinal sound waves)
biomechanical movement of the eardrum/canal


--
Paul Doherty
http://members.home.net/iqueue



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QAId : 3724647
Asker : hockey23
Subject : terminal velocity?
Private : Yes

Question : A co-worker of mine threw a penny off the empire state building the other day. Please don't ask me why. Could the force of the penny falling 114 stories kill someone at ground level? I thought that it would reach terminal velocity and the force would not be great enough, but other people think that the force would be great enough to kill someone, or severely injure someone on the ground. Can you explain?

Answer : A penny is too light and has too much surface area - as you said it will reach it's terminal velocity and carry on at that speed until it hit the person. And the speed will be relatively slow because of the penny's light weight. I'd estimate a terminal velocity of around 30m/sec which would hurt like heck, and may be enough to crack your skull, but probably not, and almost surely not enough to kill you.

Answer : One other thing - please do not ask normal questions like this as "private" questions. Doing so deprives others of reading them and defeats part of the collaborative nature of AskMe.com...

Thanks,
Paul
Rating : 5


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QAId : 3746893
Asker : icollaboDotCom
Subject : DateSet
Private : No

Question : Mr.pauldoherty,

I have had your program work successfully in test 2 times, Once on Win 2000 and on Win 95. I am now on trying to install it on a Windows NT Server machine and having all kinds of problems. I have done the follwing:

1. Installed the DATESET.EXE into C:\WINNT\system32
2. I have tried to test the following code on the machine

dateset
c:\mydate.bat
ren C:\WINNT\Profiles\Administrator\Desktop\t.txt C:\WINNT\Profiles\Administrator\Desktop\t.%MYDATE%

3. The program is running throught the process the Dos output as I run the batch file resembles

C:\Byp>bypbkup.bat
C:\Byp>dateset
C:\Byp>c:\mydate.bat

When I run the following, I get an error message that:
"The syntax of the command is incorrect." It appears to be referencing "call c:\mydate.bat"

dateset
c:\WINNT\system32\dateset.exe
call c:\mydate.bat
cd c:\
ren C:\WINNT\Profiles\Administrator\Desktop\t.txt C:\WINNT\Profiles\Administrator\Desktop\t.%MYDATE%


Adding "c:\WINNT\system32\dateset.exe" provides the same results as the first scenario? Here is that batch file...


dateset
c:\WINNT\system32\dateset.exe
c:\mydate.bat
cd c:\
ren C:\WINNT\Profiles\Administrator\Desktop\t.txt C:\WINNT\Profiles\Administrator\Desktop\t.%MYDATE%

I am totally confused? HEEELLLPPPPPP!!!!

-Brad

Answer : Try using the exact same path and filenames as in Windows 95 (where it worked) under NT - if it still fails it is something about NT and we can go from there.

--
Paul Doherty
http://members.home.net/iqueue

FUQuestion : AHHHHHHHHHHHHHH,

Anything you see wrong here? Gives me a message that: The syntax of the command is incorrect...

This is on W2000


c:\WINNT\SYSTEM32\dateset.exe
call c:\mydate.bat
ren C:\Documents and Settings\Law\Desktop\pfboae.bak C:\Documents Settings\Law\Desktop\pfboae.bak.%MYDATE%

Answer : You still need the quotes around the long paths:

ren "C:\Documents and Settings\Law\Desktop\pfboae.bak" "C:\Documents and Settings\Law\Desktop\pfboae.bak.%MYDATE%"

Also you were missing the "and" in the second parameter.

And I would also do as I suggested before and CD to the directory before renaming, like this:

c:
cd "\Documents and Settings\Law\Desktop"
ren pfboae.bak pfboae.bak.%MYDATE%

--
Paul Doherty
http://members.home.net/iqueue

Rating : 5


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QAId : 3758105
Asker : rombe3jr
Subject : Rainbows
Private : Yes

Question : Can rainbows be recreated by man without the sun, but by artificial light? If so could you tell me how it was done?

Answer : Any light source behind you, with water vapor in front of you, can make a rainbow. The chances of us having lights powerful enough to generate a sky-stretcher like a full-blown rainbow are not likely, but the same concept applies. You can create a rainbow with a flashlight and a prism.

FUQuestion : Hey I really appreciate your answer. But I am very interested in creating a minerature rainbow myself. Is there any resource that you know of that could guide me in this process?

Answer : I don't know of any web sites that detail it - try searching from:

http://www.queryserver.com

(general search)

with terms like rainbow and flashlight.

I would take a flower misting device and set it up and running, then stand back several feet and shine a Q-Beam (strong large flashlight) at the water vapor from different angles until you see the rainbow.

--
Paul Doherty
http://members.home.net/iqueue



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QAId : 3765324
Asker : Anonymous
Subject : chemistry question
Private : No

Question : what is the wavelength and frequency of infa-red light

Answer : There is a nice graphic with different frequencies of light (including infrared) and their corresponding wavelengths here:

http://www.ozemail.com.au/~swadhwa/chap2lec1.html

Infrared appears to be from 10^12 to 12^14 Hertz in frequency.

--
Paul Doherty
http://members.home.net/iqueue



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QAId : 3797022
Asker : Anonymous
Subject : I need help quickly!
Private : Yes

Question : I am doing a science fair project on light absorption and reflection on different colored popsicle stick cabins! My background research is due on Tuesday, nov. 7, and I can't find ANYTHING!! PLease help me... I am despersate! Tell me everything you know about the subjects or give me resources where I can find the info!

Answer : Any physics book will have lots of material on this - the concepts of light absorption are fairly easy.


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QAId : 3821745
Asker : mandiesr02@...
Subject : light primaries
Private : Yes

Question : 1. What are light primaries?
2. What is the difference between painters and printers primaries?
3. What happens when contrasting hues are mades similiar?

Answer : 1. "Primaries" are those base frequencies of light (or paint) that, when combined, produce (in the case of light) or remove (in the case of inks/paints) all the visible frequencies of light. Example - the primaries for visible light are red, green and blue.

2. As far as I know since both are subtractive there is no difference between paint and ink primaries.

3. I'm not sure what you are asking here - more detail please.


--
Paul Doherty
http://members.home.net/iqueue



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QAId : 3826318
Asker : ayaz05
Subject : How to determine distance
Private : No

Question : Reply me that how i can determine distance between to cities by using their latitudes and longitudes.

Bye.

Ayaz.

Answer : This may help:

Taken from - http://www.comptons.com/encyclopedia/ARTICLES/0100/01054720_A.html

"A degree of latitude can easily be changed into miles. Since the circumference of the Earth is roughly 25,000 miles, the length of each degree of latitude is about 69 miles (1/360 of 25,000 miles). Degrees of latitude vary a little in length--the variation between the shortest and the longest is less than a mile--because the Earth is not a perfect sphere but is flattened slightly toward the poles and bulges slightly around the equator (see Earth). The length of a degree of longitude, however, varies from about 69 miles at the equator to zero at the poles, where the meridians come together."


--
Paul Doherty
http://members.home.net/iqueue



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QAId : 4105552
Asker : krtina03
Subject : Psysics
Private : No

Question : Hi, how are you today? Why did scientists use a vacuum to determine acceleration of a falliing object?

Answer : Because when objects fall through a medium, such as air, their acceleration (and top speed) are affected, based on their volume and mass. If you had a bowling ball and another ball of exactly the same size but made of plastic and hollow and dropped both, the bowling ball will reach a higher top speed than the other ball. Both are accelerated by the same force of gravity, and each will accelerate at roughly the same speed up to that maximum. That maximum is called "terminal velocity" and is the fastest speed of freefall for that object. Terminal velocity is reached when an object has attained a speed such that the wind resistance encountered in the downward direction is equal to the object's weight. Since the real bowling ball has a much higher mass than the hollow one (even though both have equal surface areas - wind resistance being a funtion of surface area) it will attan a higher terminal velocity.

In the same experiment absent of air both balls will continue to accelerate at exactly the same speed, whether their masses or volumes are the same or not. The classic experiment confirming this was when the first lunar astronauts filmed themselves dropping a hammer and a feather at the same time and seeing both accelerate and hit the ground at the same time.

--
Paul Doherty
http://members.home.net/iqueue



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QAId : 4122610
Asker : Anonymous
Subject : Light waves
Private : Yes

Question : Light travels threw air and well also in a vacum but here is my question. My question is that if it travels threw a vacum it doesn't need a medium but what if there is a medium in a vacum that can not be removed?
That means it needs a medium.
Am I right?
What theory says that it doesn't need a medium when in terms it travels in a wave way.
Light waves.
Thanks

Answer : No theory is required to demonstrate that light requires no medium since we get tons of light across the void of space from our Sun. Before we could travel out into space there were theories of an "ether" that was required for light tranmission but the Michelson-Morley experiment disproved that hypothesis.

Light travels *both* as a wave and as a particle (or rather I should say it can interact as both). That is one of the paradoxes of light.

--
Paul Doherty
http://members.home.net/iqueue

Rating : 5


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QAId : 4194018
Asker : Socmomcab
Subject : Collisions
Private : Yes

Question : I don't understand this question. Could you please help me? THanks

A 2-kg ball is travelling down a pool table at 10m/s. It proceeds to collide with 2 balls that are sitting side by side that also have a mass of 2-kg with the cue ball striking the other two simultaneously (i.e. it strikes between the two balls). What is the velocity of the three balls after the collision? Please give both the magnitude and direction for each velocity. (Assume all the balls have the same radius.)

Answer : It sounds like you have a rolling cue ball that is striking two other balls that are at rest and touching and aligned perfectly perpendicular to the path of the cue ball. The question wants to know the resultant direction and speed of travel of all three balls after the collision. I would expect the two balls currently at rest will be travelling with some speed at 45 degree angles to the direction of the cue ball.

--
Paul Doherty
http://members.home.net/iqueue

Rating : 3


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QAId : 4218296
Asker : Anonymous
Subject : Rainbows
Private : Yes

Question : What shape can rainbows not look like?
How come rainbows can be in different shapes?
Thanks bye

Answer : Please do not ask questions in private if they are not of a private nature. This is a general question, and not of an embarrassing nature. Marking it as private detracts from the value of our interaction to others as they cannot read it under any circumstance.


Rainbows are only seen at specific angles from the viewer to the water, and from the water to the light source (usually the sun). The typical rainbow is a half-circle. A full rainbow would be a full circle (replacing the bottom half that is usually where the ground is).

--
Paul Doherty
http://members.home.net/iqueue

Rating : 5


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QAId : 4230647
Asker : zuetz
Subject : physics
Private : No

Question : Is the thoery of relativity proved?

Answer : As for the particularly mind-bending portion of relativity I expect you are ferring to (the time dilation effect) yes it has been proven. Two atomic clocks that are highly accurate were synchronized - one was left on the Earth and the other was flown in airplane shipments for some period of time. The relative motion between them should produce a time difference between them per the theory of relativity. Since the speeds were not appreciable when compared to the speed of light (speeds closer to light have exponentially greater time dilation effects) the difference would be still be easily measurable with such accurate clocks. Since the clock that rode on the airplanes was in motion relative to the clock on Earth it was expected that the moving clock's transpired time would be less than the Earth-bound clock and it was found to be so, thus confirming the theory's predictions.

--
Paul Doherty
http://members.home.net/iqueue


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QAId : 4230717
Asker : jontha_au
Subject : fridge magnets
Private : No

Question : Why dont fridge magnets have poles?

Answer : They do have poles, they are just not physically apparent like in a bar magnet. Even the smallest magnetic "domain" (smallest magnetic component that is the basis for all magnets) has it's own north and south pole. It is only by virtue of the fact that some materials have the majority of their magnetic domains facing the same direction that those materials are magnets in the first place. Notice that if you take an existing magnet and heat or strike it you will diminish it's magnetic strength. This isn't because there is less magnetic energy than before - it's because you have dislodged and misaligned some of the internal magentic domains so their force no longer adds to the aggregate force (their pull is no longer properly aligned to add to the overall force).


--
Paul Doherty, CNA3/CNE_4/CNE_IW/CNE_5/MCP/MCSE/A.A.Sc./B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities



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QAId : 4230832
Asker : sweet_jul
Subject : What heats faster water or sand?
Private : No

Question : What heats faster water or sand?

Answer : I must disagree with my esteemed fellow expert DanMan.

Sand will heat faster than water. "Specific heat" is ameasure of a materials resistance to change of temperature. Water has a very high specific heat, meaning it has a lot of "temperature inertia" for lack of a better term. If it is cold it takes a lot to heat it - if hot it takes a long time to cool. This is the primary reason we use water in all the ways we do. Hot water bottles stay warm longer than the same vessel filled with another liquid. Radiators of cars absorb massive amounts of heat. The best example of this phenomenon that even uses the two materials you've asked about is the beach. In the morning before the sun rises the water and sand are at or near the same temperature. When the sun comes up the sand quickly warms, making the sand burn your feet, even before the water is warm enough to swim in (this is due to sand's low specific heat - it doesn't resist changes in temperature well). All during the day the sand is warmer than the water, and all day the water is absorbing more and more radiant energy (light) and warming more and more but likely never equalling the sand's temperature. Then as the sun goes down the sand, having a low specific heat, cools quickly, while the water remains relatively warm throughout most of the night. You can easily demonstrate this entire effect by observing the breezes at the beach. During the day, when the sand is warmer than the water, the hotter air above the sand rises, to be replaced by the cooler air from over the ocean. This produces breezes that blow in from the ocean. At night the water stays warmer than the sand which quickly cools and the breeze is reversed and blows out to sea.


--
Paul Doherty, CNA3/CNE_4/CNE_IW/CNE_5/MCP/MCSE/A.A.Sc./B.A.
http://members.home.net/iqueue
Home of PC DiskMaster and other Windows utilities

Rating : 5


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QAId : 4238232
Asker : _merlyn_
Subject : why.....?
Private : Yes

Question : Hi !
My name is Ameya and am relatively new to askme as an expert on this category. Have just been exposed to a number of questions and have answered most of them.
Before I get going on further I thought it would be a good idea to get some perspective from you.
Hoping you can share your thoughts and feelings on the following questions that burn away in my mind….. out of curiosity and wonder that so many of you experts are actually here to advice and counsel all the people asking queries.

1. What are the advantages of becoming an expert on this category? i mean, what is it that makes you all spend time and energy answering all these questions? What is it that you find rewarding?

2. Is there any other place where you are an expert and what are the relative advantages here?

many thanks and warm regards,
Ameya

Answer : Hi Ameya...

1 The only advantage to becoming an expert in this (or any other) category is it makes it more ikely that (if you are highly ranked in the category) that you will receive an award if the category is picked by AskMe.com during one of their prize selections. As for myself I have won I think 4 or 5 category awards and 2 quarterly awards (cash and tshirts for each) but I began and continue answering questions not for that. When I started in Jan 2000 there were no awards at all. It was only in March or April that they began that and with it came some less than stellar new experts along with it.

I answer the questions for the following reasons:

a) I like to help people
b) It keeps me sharp in areas of interest
c) I enjoy the recognition
d) it's fun

2) I do not answer questions on any other websites, although I do participate in forum dicussions. Other expert sites will pay you for your information. These sites, however, are not as attractive for me as they usually involve you being made available by phone to someone with a problem (this is usually for computer experts). The problem with this is that, unlike AskMe, the questions and answers are not known so there is no huge database of knowledge like there is here. That is another advantage for me here - I build up a large repository of questions (almost 2000 so far!) that I've answered that I can go back and look at later.

My categories of expertise:

http://www.askme.com/viewprofile.asp?xid=50373

Best of luck to you!

--
Paul Doherty
http://members.home.net/iqueue



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QAId : 4246249
Asker : cindy_lens
Subject : stop print cover page
Private : No

Question : Hi

After downloading and installed HP printer from hp.com onto SUNS Sparc 2.7, I cannot stop the printer from printing the cover page. I accessed admintool and deselected "Always print banner", I still have no success.

Thank you
Cindy

Answer : An

lpadmin [printer name and other options] -o nobanner

should stop the behavior. Use lpadmin and lpstat [-a] to get the name of the printer to modify.

--
Paul Doherty
http://members.home.net/iqueue

FUQuestion : Hi

It still does not work. I accessed this site to install the software:
http://www.hp.com/cposupport/swindexes/hpjdprinte18924_swen.html#Solaris%207

Answer : Found the answer by going to that URL and clicking the "Solve a problem" link, then put in "stop banner page".

http://www.hp.com/cposupport/networking/support_doc/bpj02755.html


--
Paul Doherty
http://members.home.net/iqueue

Rating : 5


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QAId : 4330224
Asker : jtaber
Subject : Magnetism
Private : No

Question : Why isn't manganese ferromagnetic when it actually has one more unpaired electron than iron?

Answer : It has less to do with electrons being unpaired than it has to do with the spins of elctrons failing to be cancelled out by the alternate spins of neighboring electrons.

Cecil has the "Straight Dope" on this one:

http://www.straightdope.com/classics/a3_339.html


--
Paul Doherty
http://members.home.net/iqueue

Rating : 5


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QAId : 4413506
Asker : Anonymous
Subject : Ultra Volet light
Private : Yes

Question : Ultra Volet light carries vitiam D.
Is this true?
Someone told me and I just want to check if they lied to me again.
Thanks bye

Answer : That's not quite the way to say it. The ultravioler light doesn't contain vitamin D - it causes your skin to *produce* vitamin D. Therefore small quantities of sunshine can be beneficial.

--
Paul Doherty
http://members.home.net/iqueue

Rating : 5


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QAId : 4481137
Asker : Anonymous
Subject : Entrophy
Private : Yes

Question : Hi,

I read a good book entitled, "Hyperspace" by Michio Kaku. The author discusses many topics ranging from wormholes, parallel dimesions, hyperspace, and the eventual death of not just the earth itself but the universe as well. He mentions that in about a billion years from now our atoms will eventually return to the sun. Consider the following thought experiment:

Imagine that one scientist achieved immortality where all his cells are constantly regenerating without limitations.


1)If he lived to be a billion years old, barring injury or illness, will all of his atoms still turn to dust due to entrophy?



Dr. Kaku also stated that the universe will end in one of two possible ways:

a)It will contract and collaspe into a fiery ball

or

b)It will expand forever while all the stars in it's path will darken and end in an ice age


He has no doubt that when the earth is destroy once our sun goes supernova, humanity will take it's rightful place among the stars and collonize the galaxy. The real threat is the death of the universe. He believes that humanity's only salavation is to master the art of Hyperspace and entered it before the universe takes our species to it's ultimate doom.

2)Has it been proven at least mathematically that it could exist?

3)Obviously it would take a whole lot of energy but could humans in 4 billion years accomplish this?

regards,

Danny

Answer : As for question #1 - if we take your statement

"Imagine that one scientist achieved immortality where all his cells are constantly regenerating without limitations."

and apply it to the question the answer would be no, he would not succumb to entropy since he is already defeating entropy by our thought experiment construct of him being immortal.

2. I have no knowledge of this "hyperspace" so I can't conjecture on its existence or on question #3 which follows.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 4


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QAId : 4520826
Asker : muddgrl34@...
Subject : MAth and skiing!?!
Private : No

Question : Hi i have a question for you. I am doing a project for my highschool geometry class. I have to do a project on how math and skiing are related. Mostly, do you know what the skies have to do with math and how the design of the skies makes the skier go faster, turn better, or what not. Please get back to me as soon as possible!!

THANK YOU!!

Answer : Well just off the top of my head there are a few areas of physics that come to mind:


gravity (what makes you go down the hill ;-)
inertia (why it hurts to stop quickly)
rotational inertia (why shorter skis turn faster, and why longer skis have more stability and speed)
regelation (see my previous answer on physics and hockey for full details - http://www1.askme.com/SearchResults.asp?pm=va&AnswerRating=&cid=852&xShowNew=1&QA=on&xid=50373&query=hockey&prev=QA%2520&vid=1075481)

Let me know if you need something else on this...


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 4607472
Asker : jtaber
Subject : Liquid Oxygen
Private : No

Question : What is the surface tension of liquid oxygen and liquid nitrogen?

Answer : These are as close as I could get...

http://www.chipscalereview.com/9809/m.abtewb1.htm

http://members.spree.com/education/UVKChem/page2.htm


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 4613332
Asker : Anonymous
Subject : Watt's
Private : Yes

Question : How did they get the name watt's and how come watts is equal to V times I? I mean how come I means amps?
Thanks bye

Answer : It's named after James Watt.

http://www.dictionary.com/cgi-bin/dict.pl?term=watt

As for using I for amps I have no clue. My best guess without doing any research is that it was named after a similar concept from long ago.

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities

Rating : 5


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QAId : 4652748
Asker : Anonymous
Subject : leverage
Private : No

Question : how do you figure leverage?
for example: if you have a pole extending from a base 3 feet with 1,300 hundred pounds at the end how much pressure is at the base?

Answer : Diving the torque (turning pressure) is easy. Just take the distance from the fulcrum (point of support) to the point of the application of force, and multiply it by the force applied. To determine whether a certain weight object on the other side of the fulcrum can be lifted use the same principle. For example if the object on the other side weighs twice as much as the force being applied on this side of the lever there will need to be twice the distance to the fulcrum on the force-applied side to lift it.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 4673695
Asker : Anonymous
Subject : Science project
Private : No

Question : I measured water, soil and air heated by sunlight and found the soil retained the highest temp over the 5 day period-why? also, the air came in second for retaining heat-why?

thanks for any in put
Answer from FAQ : 2677367
specific heat capacity
8/28/2000
If by "retained the highest temp" you mean the highest average temperature over the time you measured I would say that the soil was the highest since it's dark in color and absorbed more light (less reflected). And water has a notoriously high specific heat (resistance to change in temperature) so that would explain why the air would be warmer than it.

See my FAQ I referenced below for my longer answer on specific heat of water compared to other materials.

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities



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QAId : 4675627
Asker : kinkyangel666@...
Subject : physics of bungee barbie
Private : Yes

Question : In physics we have a lab assignment, and the assignment is to figure out a way to get a barbie really close to the ground, but the barbie cannot touch the ground, to do this we have to create our own bungee cord, what i dont understand though, is how does this relate to physics?....the only solution i see, is trial and error.

Thankyou for your time and consideration

Sincerely

Angel

Answer : Nothing says physics means you predict the answer before the experiment. Sometimes if you don't know enough about the factors involved you may have to perform some runs to learn what is significant so you can then make predictions based on that info.

Seems to me suspecnding Bungee Barbie(TM) from rubber bands on each hand and tying a weight to her feet would have a good chance of accomplishing what you're after.

Let me know if you need something else.

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities



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QAId : 4714371
Asker : Anonymous
Subject : pictures of a Fluorine atom
Private : No

Question : Where can I find pictures of a Fluorine atom to help me make a model? I need answers fast!

Answer : http://www.google.com/search?q=images+flourine+atom


--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities



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QAId : 4723144
Asker : jon1149
Subject : rockets
Private : No

Question : I don't understand why rockets and space shuttles don't just topple over when taking off. Surely a slight gust of wind or a slight inbalance in the upward thrust would cause them to fall over! Can you explain this?!
Thanks

Answer : For low speeds this is probably true. Once the rockets gets moving the shape of it acts like a dart in thw wind, providing little resistance at the front and a lot at the rear (which serves to keep the back, well, in back :-)

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities

Rating : 5


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QAId : 4747923
Asker : mgindorff
Subject : acceleration due to gravity.
Private : No

Question : How far will a 20 kg rock in 5 seconds? We are
in disagreement about the answer.

Solution 1: Using 9.8 m/sec/sec= (V final- O m/sec) / 5

We came up with 49 m/sec.

Using the formula for speed we went 49 m/sec times 5 sec
and came up with a distance of 245 meters.

Solution 2: If you manually add the acceleration of gravity
You come up with 156.8 meters.

Which is correct and why?

Answer : I get 122.5 meters of fall after 5 seconds. I think you made a slight mistake when you got 49m/sec and then multiplied *it* by 5 seconds. The thing to remember that 9.8m/sec is the amount of speed *added* over each second of fall. For example if you drop a rock and let it fall one second *at the end of that second* it will be travelling at a rate of 9.8m/sec, but it won't have travelled that far. Why is that? Because at the beginning of the second it was holding perfectly still, and at the end it was travelling at 9.8m/sec with smooth acceleration all in between. So you must find it's *average* speed over that second by dividing the time in half (we're multiplying by 1/2 (.5) but it's the same thing). The formula for the distance fallen when you know the time the object has fallen is:

1/2gt^2

where g is 9.8m/sec for gravity
t is time in seconds for the fall

So when we plug in your numbers:

1/2 * (9.8 * 5^2)

1/2 * (9.8 * 25)
1/2 * (245)

= 122.5m of fall after 5 seconds.

If you want to know how fast the object is falling at the end of any particular second just multiply the gravitational acceleration by the number of seconds of fall:

5 seconds of fall:

gt

9.8 * 5 = 47.5m/sec at the end of 5 seconds


For more info see one of my questions I previously answered on a tennis shot that deals with gravitational fall:

http://www1.askme.com/MyXpertise.asp?pm=va&method=faq&cid=852&viewfaq=1&page=1&vid=3239956


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 4776025
Asker : brl
Subject : waves
Private : No

Question : Only xrays and gamma are shorter than________ waves?

Answer : Ultraviolet fits there, but there may be some shorter than UV but longer than gamma and x-rays.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 4780528
Asker : JTP22
Subject : speed of light
Private : No

Question : im a year 12 physics student and recently asked my teacher a question that he could not answer.
here it is:
if two people were BOTH traveling at the speed of light (i know that thier mass becomes infinte but just suppose)and they look at each other what would they see?

becase of properties of light (V is always constant)i dont know that answer!

would they see eachother as still?

please answer in detail.
also can you prove it?
can you give me any sites too?

Answer : This is part of how Einstein came up with the theories of relativity (general and special). He imagined what the world would look like if travelled alongside a beam of light. That conundrum nearly drove him mad but in the end it led to relativity.

Cecil Adams has a fine answer that directly relates to your question - the answer being that both observers do not know they are moving (they are in the same frame of reference) and therefore share the same time frame (they age at the same rate).

http://www.straightdope.com/classics/a3_143.html


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 4786060
Asker : sarah_luvs_ya
Subject : highschool physics
Private : No

Question : If one were to roll a steel, a glass, a rubber, and a wood ball down a wooden piece of molding and the balls were approximately the same size but had different masses I thought that the heavier the ball the faster it would go down the ramp. When I tried it didn't work out this way. Were the balls supposed to all go at the same speed? Would the coefficient of friction, gravity, or air resistance have anything to do with it? momentum? anyhting else??


Thanx

Answer : If the balls were all the same size they should roll very close to the same speed. A ramp experiment like this is merely simualting a slow-motion freefall, as if you had dropped these same balls off a building. I believe it was Galileo who first did these ramp experiments and he reasoned as above that the inclined plane (neglecting frictional forces) did not change the base concept that the balls accelerate due to gravity. And if the balls are slowed by the ramp (of course they arem in relation to how fast they would go falling unhindered) they are all slowed by the same amount. This decrease in acceleration for these "falling" objects made gravity easier for Galileo to study. The diameter of the ball can affect the speed, as can the composition of the ball. Air resistance will have nothing to do with it unless you have a long ramp to get the balls up to appreciable speed. Then air resistance is a function of surface area (all the same) and weight (different since made of different materials). Each ball will end up with a different amount of momentum, since momentum is made up of velocity and mass (and each ball's makeup is different - some materials being more massive than others).

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities

Rating : 5


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QAId : 4882276
Asker : Anonymous
Subject : Sound waves traveling
Private : No

Question : Dear Paul,

I do not have a background in physics.


My questions:

If sound waves travel, where do they go?
Would it be possible to retrieve (recall) them?

I know that these probably sound like stupid questions, but my father and I were having a discussion about this and he doesn't think that such a thing is 'far-fetched.' He feels that maybe someday scientists will be able to hear Moses's sermon on the mountain, for example.
Thank you.

Answer : I'm going to have to say that's unlikely (recovering speeches that were uttered any time ago). The reason is that sound is merely a temporary disturbance of a medium. For example when you strike a tuning fork it visibly oscillates and produces a sound. When the vibration finishes and no more sound is being generated both fork, and the air that transmitted the sound to your ears, is back in a quiescent state. No evidence of the sound will remain in the fork or the air (or your ears for that matter). The only place the sound may reside is in your memory or a recording device. Absent either of those (a listener still alive, or a recording device) it's not possible to retrieve sound that I'm aware.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 4952631
Asker : esbee123
Subject : physics
Private : No

Question : why is a turboprop engine of an aircraft affected by speed of sound whereas turbojet aircrafts fly more than the speed of sound.

Answer : Here's a discussion on the subject - apparently there is nothing that would prohibit it, but the propeller-based engine produces a horrible amount of sound:

http://groups.google.com/groups?q=turboprop+speed+sound&hl=en&lr=&safe=off&rnum=4&seld=995901438&ic=1

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities



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QAId : 4991601
Asker : RobertHeller
Subject : Gravirt assisted acceleration of spacecfaft
Private : Yes

Question : I am working on a SF novel and want to have some level of reality in it. The novel involves a Busard Interstellar Ramjet. I want to be sure I have things working realistly. I am having the spacecraft launched from the Moon (magnetic levitation railroad launcher), into a close solar orbit (about the orbit of Mercury. I understand that a Busard Interstellar Ramjet needs to get up to about .04c to be going fast enough to collect enough protons to fire up its fusion engine. I have written a C program to calculate the rate of acceleration needed to achive this speed by about the orbit of Mercury, but I am not getting 'sane' numbers. I suspect that my math is totally wrong.

I need to know for my book:

1) How much acceration the magnetic levitation railroad launcher needs to impart on the ramjet.

2) How much additional acceration the sun's gravity will add.

3) How long it will take to 'fall into the sun'.

4) How much acceration would be reasonable to maintain once the ramjet has gone around the sun and begins heading out into interstellar space and how long will it take to get as far as the Oort cloud and how fast it will be going by then.

Thanks in advance for any help.

Answer : I would expect there is only one "right" speed at which to launch the vehicle and still arrive for orbital capture at the desired distance from the Sun. Once you fall into orbit with the Sun there will be an increase in velocity due to the "gravity whip" as I like to call it - this gravity whip is precisely why I believe there is only one correct speed to approach. Approach too slow and the gravity whip will accelerate you right into the Sun quickly - approach too fast and the gravity whip sends you flying away from the Sun at higher speed. That may make a good device for you - have the maglev rocket the ship off the moon at high speed, with a trajectory calculated to "skim" the Sun for an additional boost of acceleration which brings it to the necessary speed to kick in the ramjet. Or you could stick with a "decaying orbit" idea, where once the ship has entered a decaying orbit around the Sun, it's velocity (and temp! makes for some more drama as the heat rises) continues to increase to the speed necessary to start the ramjet and escape.

Once you're off at whatever final speed you're moving at just divide the distance to the Oort cloud (30 trillion kilometers) by that speed to get the time needed for the trip.

Best of luck on the book,

Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities

FUQuestion : I understand about the 'gravity whip' idea. I just need some help calculating the amount of acceration the maglev needs to impart and how much additional acceration will be gained by the sun's gravity and how much acceration the ramjet can maintain to achive solar escape velocity.
Declined (Reason) : Can only help on the concept, not the fake math - Contact NASA for that... :-)


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QAId : 4993541
Asker : cyberpal_1@...
Subject : physics
Private : No

Question : dear expert,

iam a layman in physics, out of touch with it since school.

but iam interested in knowing about Albert Einstein's formula e=mc^2 . what do the alphabets stand for in the formula and what does it explain?

regards ,
Cyberpal.
------------------------------------------------

Answer : In the formula:

e - the total energy contained in the mass of an object
m - the "rest mass" of the object
c - velocity of light

What it says: The amount of energy in a physical object is equal to the mass of the object times the velocity of light squared.

In a nutshell what the forumula means is that energy and mass are one and the same thing. All objects are simply congealed energy, and energy contains mass. It is a "mass-equivalence" formula. If you need further information regarding this let me know.

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities

Rating : 5


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QAId : 5002266
Asker : yakkuli
Subject : how a microwave oven works
Private : No

Question : how does a microwave oven cook without any ignition or fire etc.?

Answer : Instead of a normal oven where heat is moved via conduction and convection a microwave oven works off the principle of "forced resonance". The wavelength of radio waves ("microwaves") used in a microwave oven happen to produce atomic resonaces (vibrational motion) in water and fat molecules. These motions are heat and are then conducted throughout the material. See this article for more details:

http://www.howstuffworks.com/microwave.htm


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 4


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QAId : 5002282
Asker : Anonymous
Subject : rain
Private : No

Question : does one get wetter running or walking in the rain? This is assuming that one has no umbrella.

Answer : There is no difference (amazingly I too have pondered the question! hehe). If you think about it this way running only changes *where* you get wet. By running you are catching up to raindrops in front of you (that subsequently hit your front and legs) that would normally have fallen in front of you. So by running you may find yourself soaked in front but relatively dry in the back. You can't win for losing huh?? :-)



--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5

FUQuestion : Thanks...it would make sense then that if you run, you're spending less time so you get less wet. (I ask b/c this is a bet)

Answer : Well let's compare two situations:

1) Standing perfectly still in the rain

2) Running at full sprint in the rain

In situation #1 (we're assuming that the rain is falling perfectly vertical for this discussion) you'll note that there isn't much surface area you're exposing to the rain - mostly just your head and shoulders (unless you've been partaking of the pasta a bit too much! ;-)

In situation #2 you are now exposing your head and shoulds *AND* almost your entire frontal area to raindrops, which would result in you getting at least as wet if not more wet than in situation #1 (perhaps only equal due to the lesser time during which you are exposed to the rain since you're running).

So I would still call it a draw. You guys keep your money and shake hands. :-)


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 5002300
Asker : sosoboy41
Subject : measuring volume
Private : No

Question : what are the different methods of measuring volume?

Answer : I don't know about multiple ways. The best way I know of to get the volume of an irregular-shaped object:

1) Fill a container larger than the object completely full of water.

2) Place a larger container below that one to catch the water.

3) Attach the object to be measure to a string (or if it's a bouyant object to a stick) and submerge the object completely in the top tub. This will displace water into the tub below. Submerge it slowly so no spills or extra "waves" are produced.

4) Now measure the volume of water captured in the tub below. That volume is the same as the object you submerged.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 5002317
Asker : jtucker81
Subject : momentum2
Private : No

Question : You are standing on a log and a friend is trying to knock you off. He throws the ball at you. You can catch it, or you can let it bounce off of you.

Which is more likely to topple you, catching the ball or letting it bounce off? Please explain your answer in some detail



Answer : You are more likely to be toppled if you let it bounce off of you. If you catch it the only momentum inparted is the initial momentum from the other person's throw (the ball coming to rest with you). If instead you let it hit you and bounce away you will have absorbed the initial momentum *plus* given it new momentum in the opposite direction, which means that you will experience a force equal to that negative momentum in the backwards direction.

The same concept is used with rubber bullets for crowd control. They don't get absorbed like a lead bullet does so they don't usually cause any great harm, but they pack a knock-down wallop since they rebound off the victim.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 5002321
Asker : sosoboy41
Subject : how to measure volume?
Private : No

Question : how can i measure volume

Answer : The best way I know of to get the volume of an irregular-shaped object:

1) Fill a container larger than the object completely full of water.

2) Place a larger container below that one to catch the water.

3) Attach the object to be measure to a string (or if it's a bouyant object to a stick) and submerge the object completely in the top tub. This will displace water into the tub below. Submerge it slowly so no spills or extra "waves" are produced.

4) Now measure the volume of water captured in the tub below. That volume is the same as the object you submerged.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities






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QAId : 5002365
Asker : starshine1729
Subject : Terminal Velocity
Private : No

Question : A free falling body may experience terminal velocity. Please explain terminal velocity in terms of a free falling body. Thank You!

Answer : Terminal velocity is simply the maximum unassisted speed that an object can fall in air. Two aspects of an object contribute to what this speed will be - it's mass (weight) and it's surface area (amount of the object exposed to air). What happens is as the speed of the fall increases so does the effect of the air your strike as you fly downwards. If you continue to accelerate long enough (like in a sky dive from altitude) evetually you will stop accelerating when the force of the air resistance you enounter equals your weight.

Human beings are large and thus tend to have a large volume relative to our surface area. So our terminal velocity is quite high - around 125 MPH. An ant or a feather have very little volume and tons of surface area (think of the tiny wisps that make up a feather, or the skinny legs of an ant) so their weight will be equalled at a far lower speed. The terminal velocity of an ant is likely around 3 feet per second. That's why you can drop an ant from the ceiling and he'll walk away. So that to a human and they'll be lucky to not be heading to the hospital with an injury!


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 5002411
Asker : starshine1729
Subject : Satellite Orbit
Private : No

Question : Please explane how satellites orbit the earth. Why do they continue to orbit and not fall to earth? Why do they stay in orbit and no "run off" into space? Thank You!

Answer : A satellite *does* fall towards Earth. The gravitational force at that distance is greatly diminished but it's still quite present. The Earth curves in a fairly uniform fashion - every X distance travelled horizontally equates to Y drop in altitude. At ground-level it's about 4.9 meters of drop for every 8 kilometers of lateral distance. In space the distances are greater but the concept is the same. For the satellite to experience the same rate of fall (and maintain its distance from the Earth) it needs to travel a horizontal distance during each second of fall that will bring it to the same height above the ground as it was at the beginning of the second. So in essense the satellite "falls around the Earth" rather than into it. If the satellite's speed begins to slow it will be what is called a "decaying orbit" where it is no longer travelling the lateral distance required each second, so therefore it is now is a "spiral" of sorts, losing altitude with each second. If it goes faster than is needed to maintain the orbit it will gradually gain altitude and eventually launch out into space.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 3.5
Rating : 3.5


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QAId : 5002426
Asker : Anonymous
Subject : The movement of the water
Private : No

Question : When I fill up a sink with water and let water go, the whirlpool turns clockwise. I know that this also occurs in the south-hemisphere oppositely, I would like to know what direction of the whirlpool would turn when we are in the exact North Pole or the equator.

Answer : Flip a coin and find out. Unless the water is *completely stable and non-moving* (very rare) it will have an equal chance of developing a spin in either direction.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 3


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QAId : 5002476
Asker : wto2k
Subject : why sky is blue
Private : No

Question : How come sky is blue ?
Thanks for your time !!!

Answer : The sun produces light of almost all frequencies (white light). When that light attempts to penetrate our atmosphere some of the frequencies interact more than others. Particularly the higher frequencies of blue and ultraviolet (just above our range of perception). They set off sympathetic virations in the atomic structures of the various molecules that make up our air and these atoms in turn release photons of light in the same frequency range. Much like a bunch of tuning forks setting each other off. This scattering effect is what colors the sky blue, as those atoms respond to the frequencies closest to their own. Interstingly, if you could see ultraviolet light with your eyes you would find that the sky is actually ultraviolet in color, not blue since ultraviolet has the highest resonance with the air molecules.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 4


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QAId : 5024883
Asker : bandhani
Subject : heat
Private : No

Question : 1)Why burning by steam is severe than hot water while both attain same temperature ?

2)what is the difference between latent heat and specific heat ?

Answer : 1) A steam burn is worse because it contains the extra energy that brought the water from a liquid to a vapor state (and a vapor state is more "energetic" than liquid of the same temp) - specifically 540 calories per cubic milliliter more, if memory serves me.

2) http://www.sasked.gov.sk.ca/docs/midlsci/wwwboard/messages/3845.html


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 5144382
Asker : Anonymous
Subject : INSULATING PROPERTIES OF VARIOUS MATERIALS
Private : Yes

Question : My 5th grader is doing a sci fair project. He's testing 5 different cups (clear glass, foam, paper, plastic, stoneware)to see which will keep water hottest over a 20-min. period. He must write an accompanying research paper. Where can he find info on the insulating capabilities of these various materials? He's also stuck on what the control should be. Any help or advice would be much appreciated.

Answer : In my opinion no resources on the insulating proerties is required as that is the point of his research. He will be discovering their properties and that is the point of the experiment.

I would suggest that he have the 5 cups being tested (identical size and shape and amount of water in each, poured from the same kettle so the water is identical in temp). As for the control I would look for a *metal* cup (like a metal measuring cup), as it has no insulating properties to speak of, and will bleed off heat at the highest expected rate. All the other cups should retain at least as much if not more heat than the metal cup and so the metal cup will serve well as a comparison point.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities


Rating : 5


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QAId : 5147211
Asker : honey006
Subject : physics
Private : No

Question : How did Galileo apply his experimental results (from using a ramp) to describe the motion for a falling object?

Answer : He (correctly) believed that the two situations are analogous: if two objects are dropped in freefall or rolled down an inclined plane the force of gravity is the same in both cases. The only thing the plane does is give you "freefall in slow motion" since the only other force present (in equal amount) is friction.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 4


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QAId : 5169619
Asker : Starfury77
Subject : Reaching Infinite Energy
Private : No

Question : Hi. It is known that for mass to reach light speed, the energy requirements would be infinite. Since matter and energy are both the same thing that means that the ship's mass would become infinite as well.

Does infinity, in physics, means nothing, and cannot exist? Will it always be unatainable no matter how advance we get?

Juls


Answer : In a nutshell you're right on - it is not possible (with our current understanding of the Way Things Are(tm)) for an object with non-zero rest mass to travel at the speed of light for the reasons you stated.

http://www.physlink.com/ae180.cfm

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities

Rating : 4


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QAId : 5182097
Asker : Anonymous
Subject : quantum mechanics
Private : Yes

Question : Hi...My name is Sarah, and I'm tutoring a grade 12 physics student. Unfortunately I have a question that I don't know how to answer...could you please help?

Question is:

How many different states are possible for an electron whose principal quantum number is n=4?

* Sorry no answer is provided...

Thank you!

Answer : I don't know this one, but I found some good resources for you:

http://www.edpsciences.org/articles/epjd/pdf/2001/02/d0203.pdf

http://www.bcpl.net/~kdrews/mtas/modern2.html

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities

Rating : 4


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QAId : 5219957
Asker : amshowman
Subject : clothes on a radiator
Private : No

Question : Hi,

Please can you help me with the following problem.

If you put wet clothes on a radiator in an normal sized room, will the average temperature of the room be lower than if the clothes were not there.

Thanks a lot,

Andrew

Answer : Assuming the temperature of the clothes matched the ambient temperature in the room when they were brought in I'd say no. Some of the heat from the radiator that would have gone directly into the air will now go to helping the water in the clothes undergo a state change to a vapor state. This will increase the humidity in the room which increases the perceived temperature to human since the water vapor will condense onto your skin, thereby state-changing back to liquid and giving up the excess energy to your skin. But that water was state-changed into vapor by heat that would have been brought into the room by the radiator anyway so I don't think there will be a net effect on the average temperature in the room as a whole.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 5269988
Asker : Jakathrea
Subject : Light, and Speed
Private : Yes

Question : Hi,

I was wondering if i'm on a train going the speed of light, and i run from one end of the train to the other end, from the frame of reference of one standing on the platform, am i going faster than light?

I'd appreciate detailed answers, and if it isn't possible, i'd like to know why. If equations are in the problem, then do explain them. Thanks.

Jak

Answer : No you would not be seen to be moving faster than the speed of light due to the fact that the observer would see time standing absolutely still in your frame of reference from his. Not to mention that anything with rest mass cannot travel at the speed of light since as you accelerate towards the speed of light more and more energy goes towards making the object being accelerated more massive (thus requiring even more energy to accelerate further).

More related information:

http://www.tufts.edu/~ndanie01/relativity.html

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities

Rating : 3


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QAId : 5284826
Asker : Anonymous
Subject : spectral lines of the element hydrogen
Private : Yes

Question : Hi! I just finished conducting a lab involving spectral lines of the element hydrogen....And I have a big question....I need to do a formal lab write-up....How do you do a formal lab write up? I have to do an introduction that is one page long...can you help me? do you know any web sites that have an example of how to do a lab write up? I need an A it's my ISU...thanks a bunch!


Answer : Here is some advice on the subject:

http://www.physics.lsa.umich.edu/IP-LABS/geninfo.html#labreport

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities



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QAId : 5315088
Asker : Anonymous
Subject : How do colors affect our moods?
Private : Yes

Question : Hi,
Do u know how colors affect our moods?
I need to do my papers on this, so plz help me..
thx.

Answer : This belongs is Psychology, not Physics but luckily for you I'm degreed in Psychology. ;-)

Here are some good resources about this effect. Psychologists,building planners and interior designers have long known that color can affect people's moods and behaviors.

http://www.infoplease.com/spot/colors1.html

http://www.para.com/pages/color/psych.htm

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities

Rating : 5


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QAId : 5347229
Asker : pak88
Subject : mechanics
Private : No

Question : what is an inertial fram of referens?
pleas i'm much concerned about the mathematical
aspect of it all. you can also give further
information if you choose?

Answer : An intertial frame of reference is also known as a "non-accelerating" frame of reference. This construct is useful is deciding who is the observer and who is observed, since there is no point of absolute reference.

The quote below is from:
http://www.phys.uidaho.edu/~pbickers/Courses/310/Notes/book/node10.html

"An inertial (reference) frame is one in which any object initially at rest with respect to its surroundings, but free of external influence, remains at rest. An inertial observer is one in an inertial frame."

Paul Doherty
Rating : 4


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QAId : 5395856
Asker : scoot_saved
Subject : speed of light
Private : No

Question : I'm thinking of writing a story that will involve space travel. However, I do not want to be like other science fiction books, which make ships go faster than light with no scientific basis. Please give me different theories of how to travel faster than light, and how this might possibly be accomplished. I would appreciate it a lot.


Answer : I can't really give you any because everything I know about physics says you can't. If I were writing a book I'd probably take the "tachyon drive" or "wormhole" constructs and run with them.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 5414457
Asker : tedibarr
Subject : your specialty...physics
Private : No

Question : Hello. I am doing a physics experiment for school and my experiment will be on my trampoline. I was thinking about having an experiment dealing with the force and height of an object, those two being my variables. Yet, I really don't know how I can do the experiment or what constants should be involved. I would really apprieciate it if you gave me some tips. Thanks you.

Answer : I would think you could demonstrate the concept of momentum nicely here. Your constant(s) should be the height from which you drop objects and the actual size of the objects being dropped. Dropping objects of various masses and measuring how high they bounce on the first bounce may serve to demonstrate that more massive objects (like a bowling ball for instance) have more momentum at the same speed (all objects accelerate at the same rate until air resistance becomes a factor).

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities

Answer : Don't forget to rate the answers you receive on AskMe.com...



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QAId : 5449380
Asker : collyer@...
Subject : electricity
Private : No

Question : How do I calculate the # of amps a certain amount of (electrical) audio gear will draw, given I know the wattage of power consumption each item has? This is USA, 117volt gear.

Answer : Watts = Volts x Amperes

So with your numbers:

known_watts = 117 x unknown_amps

Now divide both sides by 117 and the result is the amps.

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities

Answer : Don't forget to rate the answers you receive on AskMe.com...

Rating : 5


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QAId : 5480380
Asker : Anonymous
Subject : Light
Private : No

Question : Can you explain refraction of light?

Answer : Refraction occurs when light waves do not travelling in a perfectly-perpendicular path through a transparent medium like glass or water. The effect is that of "bending" of the light such that the arrival point the light eventually strikes is not in a direct line from where it entered. The classic example is that of the fish floating in a bathtub of still water. When you stand outside the tub and look at the fish he appears to be floating several inches below the surface when in actuality he is much deeper in the tub than it initially appears. Why this happens is due to the speed of light through each medium. In air light travels nearly as fast as in a vacuum - around 99%. In water it travels much slower - around 75%. What happens in refraction is that light takes the *shortest time path*, no the *shortest distance path*. Since it travels slower in the water the light travels from the fish in a more directly-upwards manner whereupon it exits the water and then curves back into the direction of travel. Since your eye sees light as a line-of-sight phenomenon you see the fish as being where the light rays strike your from, rather than where he is. It's a bit hard to describe without pictures but here's a good analogy that helps a lot. Think of the front of the light wave as a wave-front that has width like one of those old push lawnmowers with the blades. It took a lot of effort to move the mower when it was pushing through grass you'd neglected to mow for the last 4 weeks. :-) But when it was on the sidewalk it moved much easier. Now imagine you were pushing it along the sidewalk and then angled it a bit to the right so the mower entered the grassy area - what happens as the right edge "bites" into the grass? What happens is that the mower is pulled even further to the right that you had it but once the whole mower is on the grassy area you plow straight ahead without change. Now imagine you reach the far side of the rectangular grassy are you were traversing. The right edge will still be leading as you exit onto the pavement and what happens then? The right edge speeds up slightly and by the time the mower exits fully onto the pavement the right side will have advanced a bit further changing your angle back to the *original angle you had upon first entering the grassy area on the other side*. So what happened is you had one angle on entering and your right side slowed down, which pulled you closer to the perpendicular by a few degrees (the taller the grass ("the denser the medium") the more your course was altered). Then you traversed the grassy area at this angle and with a slower speed. Once you reached the far side and began to exit the grassy area onto the pavement your right side sped up and by the time the whole mower was off the grass you were back at your original angle of travel. This is what light does when it travels between two different mediums. When it strikes a slower moving medium it bends towards the perpendicular, travels more slowly through the medium, and then exits at it's original incident angle.

So since we know that light bends in towards the perpendicular on *entering* a denser medium it stands to reason that upon *exiting* a denser medium it will bend *away* from the perpendicular. It does and this is why our fish appears to be higher than he is. The light travels more vertically as it traverses the water, and upon striking the surface (think mower exiting the water) it bends away from the vertical and to your waiting eye. Since your eye sees light as a "straight-line-only" affair you see the fish as being directly where the light appeared to come from.

Drawing this out on a piece of paper will help you understand it even better. Just draw a line for the water, then a fish somewhere below, an eye to observe it, and then draw the light path imagining the light working hard to get through the water (grassy area) and speeding up as it exits into the air and you will find that to get the beam to the observer's position will create a false image of the fish higher than his true position.


--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities

Answer : Don't forget to rate the answers you receive on AskMe.com...

Rating : 5


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QAId : 5507118
Asker : rhenstridge
Subject : physics
Private : No

Question : Just wondering if you could help with this question??


Bob and John got into a fight in outer space.As they pushed against each other, Bob flew off with a velocity of 1.25m/s, while John recoiled with a velocity of 3m/s in exactly the opposite direction. Find the ratio of Earth-Weights of the two men.

Answer : You almost have the answer right there - the men will move with equal momentum after the shove so since their velocities (mass x velocity = momentum) are different we can conclude that their masses are different. Just take a ratio of 1.25 to 3.0 and work it to a 1:<something> ration and that will be the relative masses of the two men (the more massive of the two men being the one who was moving slower).


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 5560513
Asker : Josue4000
Subject : physics
Private : Yes

Question : Hello I don't fully understand these question .Hopefully you can help me.

The power of an average person compare to an average working Horse is larger..But Why?

1)An olypic marathon runner can maintain a speed if about 20km/h for about 2 hours.Assuming he is 60kg inmass. How much power must be maintained?


Answer : I would say the horse's power doesn't increase as much as his bulk does. IOW a human might weigh 1/5 of what the horse weighs but might be 1/4 as powerful. Therefore the human has more power when compared in terms of mass.

As for the second question I'm not even sure how to formulate such a question - are they looking for the amount of caloric energy? Before or after digestion and the losses incurred there?


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QAId : 5622488
Asker : Anonymous
Subject : refraction of light
Private : No

Question : Hi, I was wondering if someone could answer a question for me. Define the refraction of light, and give examples.
Thanks.

Answer : See my previous answer:

http://www1.askme.com/ViewRatings.asp?pm=va&xid=50373&cid=852&page=1&vid=5480380


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 5623878
Asker : monicabenito@...
Subject : speed/distance/time
Private : No

Question : when it says for example find the time in km if a car travels 18m/s what do you do? do you do 18x60x60=64800/1000=64.8 is it right is it how you do it? find the distance divide by 3600(60x60) ues please if you could answer today cause tomorow i have a test and i need to know.
thank you very much.

Answer : Yes if the speed is given in meters per second and the distance is in kilometers you will need to convert one to the other before you can calculate the time.

18m/s velocity

travelling 20km (20 * 1000 meters per kilometer) equals 20,000 meters.

Now you can divide 20,000 by 18 to see how long the trip would take.

--
Paul Doherty
http://members.home.net/iqueue
Home of DOS/Windows Utilities




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QAId : 5719602
Asker : jugador134
Subject : Standing waves and interference
Private : No

Question : I am having trouble understanding standing waves and interference. If you could could you provide me with a conceptual understanding and perhaps a little groundwork for the problems I am having trouble with

1.) Interference
- Two loudspeakers are placed above and below another and driven by the same source of frequency at 500 Hz. (a) What min distance should the top be moved back in order to create destructive interference. (b) Assuming the top is moved twice the distance in part a, will constructive or destructive interference occur?
- Two speakers are driven by a common oscillator at 800 Hz and face each other at a distance of 1.25 m. Locate the points along a line joinging the speakers where the relative minima would be expected. (use 343 m/s for sound in air)

2) Standing waves
- A stretched string fixed at each end has a mass of 40 g and a length of 8 m. The tension in the string is 49 N. (a) Determine the positions of the nodes and antinodes for the third harmonic (b) What is the vibration frequency for this harmonic?

- Two pieces of steel wire with identical cross-sections have lengths l and 2l. Each of the wires is fixed at both ends ad stretched so that the tension in the longer wire is 4 times that of the shorter one. If the fundamental frequency of the shorter is 60 Hz what is the frequency of the second harmonic in the longer wire?

Thank you for all your help and support this year. I really appreciate it.

Answer : The idea in question #1 is that you will need to find the wavelength of the sound wave to decide the distance to move the speaker to create interference (destructive interference would happen most strongly at 1/2 the wavelength at this frequency). Since the wavelength times the frequency equals the (relatively) constant of the velocity of sound you can calculate the wavelength like this:

343 (m/sec) = 550 * X

Solve for X and you will have your wavelength. Then take half of one wavelength and you will have your distance to move the top speaker to create destructive interference.

I'm not sure how to work the #2 questions, but the one about the metal strings I think I can make a stab at. When you double the length of the second string it would normally halve the frequency. But since you've stretched it four times as tight (assuming each 1X stretch brings the sound up an octave) you will now have the longer string at double the frequency of the shorter string. I could be off here but I think that might be right. So then the shorter wire has a fundamental of 60Hz, then the longer wire's fundamental is 120Hz, and it's second harmonic would 240Hz.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 5741284
Asker : Periferique
Subject : E=MC^2
Private : Yes

Question : Sir,
I wonder if you could be kind enough o explain to a Neandethal what was the practical reult of Einstein's Theory of Relativity other than nuclear engineering. Is it relevent in my daily life? or is it more etherial, to do with just understanding the way things are?

I look forward to your thoughts and thank you for your time.
Yours very respectfully,
Periferique.

Answer : I would say it has very little impact on a person's daily life, which may explain why the concepts involved are so difficult to grasp for many laymen not familiar with the ideas. So I would say that is more important with regard to "knowing how things really are" to a layperson not working in the field (which includes me).


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5
End :


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QAId : 5751030
Asker : musicmkr84
Subject : diamagnetic levitation
Private : No

Question : Hi,
I am doing a physics project on diamagnetic levitation. I have an demonstration worked out using carbon graphite blocks, a rare earth magnet, and ceramic magnets.

But, my question is..why does the magnet levitate?? I can find some basic information, but no specifics about this subject.

Thank you for your time,
Allison

Answer : Diamagnetic materials emit an opposite-directed magnetic field when they themselves are exposed to a strong magnetic field. See these sites for pictures and examples:

http://www.fieldlines.com/other/diamag1.html

http://www.fieldlines.com/other/diamag2.html

http://home.earthlink.net/~lenyr/levmag.htm


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 5760912
Asker : Anonymous
Subject : anti-freeze
Private : No

Question : How does ant-freeze work?

Answer : Anti-freeze adds an ingredient to regular water that modifies it's boiling and freezing temperatures, making it need to be hotter for boiling, and colder for freezing. It extends the range of useful temperatures that the mixture can withstand.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 5761023
Asker : Anonymous
Subject : specific heat
Private : No

Question : Which substances heat up quicker- low or high specific hea substances? And why?

Answer : Specific heat is a measure of how much a substance *resists changes in temperature*. That means a high specific heat substance (like water) will stay cold or hot longer than a lower specific heat substance. So if you think of it like inertia applied to temperature I think you'll have the right idea.

A good example to get the idea across is the beach where you have two substances with different specific heats - water and sand. During the day the sand and water receive equal amounts of sunlight. But the water has a high specific heat and thus resists change in temperature to a greater degree than the sand. That's why the water is still usually cold and the sand will burn your feet. This is also why the air currents during the day at the beach typically consist of the wind blowing in from the ocean as the hot air over the sand rises and is replaced by cooler air over the water. At night, when the sun goes down, this trend reverses itself, with the sand cooling faster than the water (again, specific heat at work here) the water stays warmer than the sand and the breezes blow out towards the ocean.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 5916388
Asker : girl2women
Subject : Measuring the speed of light
Private : No

Question : A ten year old asked how is the speed of light measured. I didn't know and won't know until I hear from you. Can this be done at home. For a elementary school project maybe?

Answer : I don't know of an easy way to measure it (in a concrete way that students would appreciate). The last link below has a way to set it up as an experiment with a fast PC and an oscilloscope.

Theory of measuring the speed of light:
http://www.colorado.edu/physics/PhysicsInitiative/Physics2000.03.99/waves_particles/lightspeed_evidence.html

http://www.what-is-the-speed-of-light.com/early-thoughts-speed-of-light.html

http://www.what-is-the-speed-of-light.com/travelling-at-the-speed-of-light.html

How to setup an experiment:
http://www.picotech.com/experiments/speed_of_light/


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 5925823
Asker : falconusaf
Subject : Ultraviolet radiation and tanning
Private : No

Question : What percentage (if any) of the burning (tanning) rays of ultraviolet radiation is lost when using a screened in pool vs an open pool?

Answer : The few pool screens I could find appear to be just metal mesh screens of a fine nature. Ultraviolet is such a short wavelength that, unless you are using a coated glass or plastic as your screeing material (perhaps just in the roof would be good, with screens on the sides?) that I can't see it blocking any significant amount of UV radiation.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

FUQuestion : It's odd though that I spent only 45 minutes at the beach and received a substantial sunburn, but can spend 2 hours at my pool (under the screened area) and not get a sunburn. Are you sure the wavelength is not disrupted by the 1.0 mm screen width?

Answer : I can't find any more definitive info on the subject and the manufacturer's page I initially saw didn't seem to mention UV protection (wouldn't they emphaseize it if it did?). Nonetheless your evidence from your personal experience sounds compelling and you may be deriving some benefit from your screen. But I really can't say how much. Wavelengths of light (including UV) are measured in billionths of a meter. I would think that since you can see through your screen with the longer wavelengths of visible light, that UV, with its shorter-still wavelength, would have little trouble penetrating.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 6026798
Asker : soheb_akhtar
Subject : project
Private : No

Question : PLEASE GIVE ME NOTES ON HAZARDS OF RADIATION

Answer : Here are some effects as related to NASA spaceflight:
http://www.nas.edu/ssb/besrch2.html

Here are some on general nuclear radiation:
http://www.ratical.org/radiation/NRBE/NRadBioEffectsP.html


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 6109135
Asker : marioricardo
Subject : study
Private : No

Question : would you think it would be wise if I studied cemical physics (I dont' know if that is how you say it, it's chemistry+physics).

WOuld I be studing until I'm 1,000 years old?
what could I do with that knowledge?

Answer : With proper choice of elective credits (and based on whether you major/major or major/minor in each area) you may not take all that many more classes (maybe only 3 or 4 more than a normal degree).

I'd think you could work in research, or in the pharmaceutical industry with such a background.
Rating : 3


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QAId : 6168313
Asker : Anonymous
Subject : magnetism
Private : No

Question : can you give me sites on magnatism. i want to do a project on the same so please if u could give me some ideas...

thanx.

Answer : http://www.howstuffworks.com/search/index.htm

Type in "magnetism" and search - I found quite a few that way.


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QAId : 6198097
Asker : japanese_man@...
Subject : physics questions
Private : No

Question : Hi I was wondering if you can tell me, does computer science utilize any physics knowledge or concepts? Is physics important for computer science? Thanks

Answer : Physics knowledge is always helpful, but it would only be truly necessary when understanding the electronics of a computer/network system, or when you are programming an application that simulates real-world conditions (gravity, inertia, friction, etc).

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5
Rating : 5


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QAId : 6214611
Asker : Anonymous
Subject : how long to get to the speed of light
Private : No

Question : how long would it take someone that is 180lbs to get to the speed of light without the G's of speeding up killing him/her?

Answer : Determine what you think the maximum acceleration the human body can withstand (person sitting vertical, perpendicular to the direction of acceleration is best - think "rocket sled"). The reason you want them perpendicular is so the "Gs" don't affect the travel of blood to the brain and back. So these aren't Gs as in a jet plane pulling maneuvers; there are G's as in pressure against the chest and abdomen, of which you can take significantly more.

Once you have your maximum acceleration rate per second, then divide the speed of light 186,000 miles per second (may need to convert miles to feet or whatever unit you're using for acceleration) by your rate of acceleration per second. If you can assume uniform acceleration (not necessarily a given as there will be losses) you will have your answer.

For example, let's assume 500 feet per second was the maximum acceleration per second we could stand.

Light speed = 186,000 miles per second

186,000 x 5280 (feet per mile) = 9,820,800,000 feet per second

9,820,800,000 / 500 = 1964160 seconds of acceleration, or 22.73 *days* of that level of acceleration. Kind of puts the speed of light into perspective!

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities





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QAId : 6240503
Asker : JTP22
Subject : conductors / tempreture
Private : No

Question : Dear Sir

I will be preforming an experiment in class this next week, yet I’m not sure how to preform it properly or t a high scientific standard. As this is an important final year high school task, I would like to ask for your professional help so that my work is on the right track.

I will be investigating the effect of temperature on the resistance of a conductor.

As I will be using normal school lab equipment, obvious cannot gain effects such as superconductivity.

· What other effects do you think can be tested?
· Do you think that the only way to find the effect of temperature on the resistance of the conductor is by in class is by heating the conductor as thereis limited equipment in class?

Normal lab equipment will be available for the experiment, EG: transformer, voltmeter, ammeter, Bunsen burner etc

1. What are the effects of heating a particular conductor with a Bunsen burner?
2. Can you please tell me how I can preform this experiment (the method) and what I would use to find the effects?
3. How would you recommend me to present my information (format)?
4. What effects or phenomenon will occur with the change in temperature (scientifically speaking)?
5. Can you provide me with some sites also that deal with this issue?

Thanks for your time; I appreciate if you can answer my questions if you have time. I know that I am asking for a grate deal of information, but I really need professional advice to preform this experiment correctly.

Sincerely
Kaveh Karimi

Answer : You will expect the resistance to increase after you heat the conductor. An excellent link with diagrams that explains why a heated metal has more resistance:

http://www.sciencejoywagon.com/physicszone/lesson/07electr/resist/default.htm

Depending on what your teacher is requiring I'd say the easiest way to perform this experiement would be with a thin bar or other piece of metal suspended between two wooden blocks so it sits a foot or so off the table (so the bunsen burner can hit it). Then take initial measurements of resistance with a normal Ohm/Volt meter at room temerature. Then heat the metal with the bunsen burner for a minute or so and take another reading of the ohms of resistance - it should be greater. You can also involve a thermometer by strapping one to the metal rod you can show how much resistance changed and what temperature change was associated with it.

Here are some resources:

http://www.deutsches-museum.de/ausstell/dauer/physik/e_wider.htm

http://www.frontiernet.net/~jlkeefer/resistemp.html

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 6241268
Asker : tahiti18
Subject : lenses
Private : No

Question : hi

i have this lab on "how to find the focal length of a combination of lenses". cud u suggest some web site which contains info on this particular topic?

thanks

Answer : Here are some good hits:

http://www.google.com/search?q=focal+length+lenses+combined


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5
End :


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QAId : 6262579
Asker : ckinsung
Subject : inertia
Private : No

Question : I stood on a train while the train was galloping with the speed 10 m/s. I jumped until 2 meter up the train and 2 seconds later I squatted down to avoid injury. In an inertia frame of reference, I was still in the same place and this is what we call as inertia. Could you explain why and how it happens as this is quite unimaginable.

Thanks.

Answer : Are you asking why you can jump up 2 meters and landed right where you jumped? If so then that is not quite true. You landed where you were *with respect to your frame of reference* (the interior of the train). With respect to the environment outside the train you travelled an equal distance as the moving train, in the same direction as the train.

What you described is indeed inertia. In the absence of a retarding force (like air resistance) or an interfering force (like the train was accelerating around a corner - remember acceleration is a change in velocity (which includes direction as well as speed)) you will continue at your current state of motion, be that at rest of moving.

If you need something further ask a follow-up question at the bottom.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

FUQuestion : Do you mean without air resistance while the train is moving under a constant velocity, I can come back to the same place? I think now I got it with Newton Laws of Motion.

Thanks.

Answer : Yes, exactly. There is no air resistance to speak of since the train is in constant motion and is assumed to be sealed (not exposed to wind). Plus the fact that you are jumping straight up and down so air resistance in the up/down direction will do nothing but slow your rise or fall and will not impact where you land on the train (which will be where you jumped from).

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities
Rating : 5


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QAId : 6290684
Asker : tvc15
Subject : Quarky
Private : Yes

Question : Wuy is it that so intelligent a fella, a BattleTech Universe aficionado and all around GREAT guy such as yourself has refrained from joining your comrades amidst yon MechWarrior 4 frey?

:)

Just had to pester. Love the work you do, man.

Highest regards and respect rendered,

Markham Abbott
aka
/FÂ\ RoverCop

Answer : Hehe, Rover bro!

Thanks for visiting me! I never got as much into MW4 as BZ - every fight seemed to degenerate into a slugfest. It lacks (for me) the subtleties of Battlezone.

Please come back and visit me anytime!

Paul Doherty
aka
/FÂ\ Merlin
Rating : 5


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QAId : 6323028
Asker : oddabe83
Subject : question on archimedes principle
Private : No

Question : Hi,
When immersed in sea water of density 1030 kg/m3, 24.0m of a supertanker is beow the water surface. What will the below-surface depth be when it enters fresh water of density 1000kg/m3, assuming the supertanker has vertical sides?

I tried to solve it foro a very long time but to no avail... please help!!

Answer : I'm not that great at math problems but understanding it conceptually has helped me come up with what I think is the answer.

We know that salt water is denser (1030) than fresh water (1000), right? Therefore since we know that a ship's bouyancy is produced by the weight of the volume of water it displaces, and salt water is denser (per volume) than fresh water is, that the ship is floating HIGHER (lower below-surface depth) in salt water than it will be when put into fresh water.

Knowing that, I found the ratio of the two densities to each other:

1030 / 1000 = 1.03

Now I took the depth from the original situation (24) and multiplied it by the difference in the densities (knowing there would be an inverse relationship between salt water and fresh):

24 x 1.03 = 24.72

Meaning the ship will float .72m deeper in fresh water than in salt.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 6361746
Asker : diop2
Subject : Lightyears
Private : Yes

Question : The diameter of our disk-shaped galaxy, the Milky Way, is about 1.0 X 10^5 lightyears. The distance to Messier 31 -which is Andromeda, the spiral galaxy nearest to the Milky Way-is about 2.0 million lightyears. If a scale model represents the Milky Way and Andromeda galaxies as dinner plates 25 cm in diameter, determine the distance between the two plates.

I know the answer is 5.0 cm, but I cannot figure out how to arrive at that answer. I first change lit.yrs to cm and this is where I got stuck.

Thanks
G

Answer : Hmmm let's see.

It seems you just need to make a ratio type of comparison between the values of the diameter of the Milky Way and it's distance to Andromeda (both in light years) to the size of the plate representing the Milky Way.

So:

10^5 = 100,000


100,000 25cm
--------- = ------
2,000,000 x

Convert the light year values to cm and solve for x (for example I get 9.461e^22 for 100,000 light years into cm).
Rating : 5


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QAId : 6382122
Asker : ruby_red
Subject : law of conservation of momentum
Private : No

Question : Please explain the following using the law of conservation of momentum:

a) a cannon recoils when fired

b) two ice skaters move apart when one pushes the other

c) an astronaut moves backward when throwing a hammer in space

d) a balloon will fly around the room when filled with air and released

Answer : In all cases each object is pushed in the opposite direction by the same amount of momentum.

In the case of the relatively massive objects (like the cannon and the astronaut) the movement they incur is slight, while the other object (cannon shell and hammer) travel with an equal momentum. Since their mass is less, and momentum equals mass times velocity, they travel at a faster speed for an equal momentum.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



Answer : Don't forget to rate the answers you've received.

Thanks,
Paul Doherty
Rating : 4


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QAId : 6442899
Asker : Anonymous
Subject : Physics
Private : Yes

Question : I'm a freshman in college and am
having difficulty with the basic material. As far as velocity vs. instantaneous, Newton's Laws, and was wondering, if you could recommend a textbook or book that would make learning the material easier. We are
currently using a textbook by Giancolli.

Thanks

Answer : For picking up the concepts in the best way, my favorite resource is "Conceptual Physics" by Paul G. Hewitt.

http://www.amazon.com/exec/obidos/ASIN/0321009711/qid=999651316/sr=2-1/ref=aps_sr_b_1_1/104-0496616-8360768

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 6516985
Asker : Anonymous
Subject : specific heat capacites
Private : No

Question : What is meant by the word 'specific' in the term 'specific heat capacity'?

And when taking the temperature of heated liquids, why do we use polystyrene cups instead of beakers?

Answer : I don't know what the word "specific" is doing in "specific heat", but without it it's just "heat" and that would be confusing now wouldn't it? ;-) I expect it's "specific" because it relates to that specific material, and is a measure of that specific material's resistance to a change in temperature.

I expect they use an insulator instead of a beaker to minimize interference from heat exchange through a glass beaker, although I can't be certain.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 6539083
Asker : Anonymous
Subject : physics
Private : Yes

Question : What is the different between matter, antimatter and dark matter?

Answer : All are explained here:

http://www.msms.doe.k12.ms.us/ap_physics/faq/modfaq.html

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 6548864
Asker : curious_fellow1
Subject : Kinematics graph
Private : No

Question : When a ball is thrown up into the air, then falls back down and the person caught it. Would its velocity-time graph looks an open-down parabola? But how will its displacement-time graph looks like?

Answer : Yes it would be a parabola.

If you're referring to its horizontal displacement, it's a straight line, unaffected by the fact the ball happens to be moving up or down (the vertical component doesn't affect the vertical(gravity) component).

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Answer : Don't forget to rate the answers you've received.

Thanks,
Paul Doherty
Rating : 2


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QAId : 6553191
Asker : allen82
Subject : other
Private : Yes

Question : From the Founders of GlobeAlive.com “World’s 1st LIVE Search Engine”

We are currently seeking experts for a pioneering web site, set to launch as a preliminary beta-test at the end of this week, and, if successful, to become fully operational this winter.

(However, we need to clarify that we are not attempting to take anyone’s attention away from AskMe.com, which provides an incredible service to which we expect to refer a large number of our own visitors.)


Called GlobeAlive.com, the web site will be introduced as “The World’s 1st LIVE Search Engine.”

For the first time on the web, a search engine visitor will be able to type in their question or request in the “Search” box and get an immediate chat response right on their screen. The response would come from a LIVE expert— perhaps yourself, should you be available online and should the question fall under your area of expertise. (Live experts would come and go online entirely at their own convenience.)

We believe that in this difficult time what internet users need is live people in real-time, not automatic directories and static web pages, to help answer their most pressing and immediate questions. We hope you agree.

As a Globe Alive expert, you would have the choice of “pushing pages” (automatically making a web site appear on the visitor’s screen with their answer) or answering the visitor in the GlobeAlive.com chat box, or both.

During the initial beta-test period, all Globe Alive experts will essentially answer live questions online in their spare time at home or at work whenever they wish. Although we won’t be able to afford to pay experts during the initial beta-test period, we encourage experts in business for themselves to use their chat sessions with visitors at Globe Alive to generate sales leads for themselves.

However, if the beta-test proves successful, and GlobeAlive.com attracts adequate investment capital— other forms of compensation, such as commissions, stock, promotions and participation in company decision-making will be considered for those experts that help us out during the beta-test.

Furthermore, given the infancy of our enterprise, the experts that participate in the beta-test will be given the opportunity to become honorary co-founders for free if they wish and naturally will be first in line to share our success should GlobeAlive.com have the impact we envision.

If you are interested in participating, or just want to check us out, please try the following:

1. Go to www.globealive.com

2. Type in “hello” or anything you want in the search window.

3. Click on “Submit,” which is right next to the search window.

4. Click on the “Live Help” button (it’s small but it should be clear).

5. Enter your email address (you can make one up if you prefer), then type in your first name (just your first name, it won’t work with two words).

6. Type in “hello” or anything you want in the chat window and click “Send”

7. One of our online experts should notice you at this point and respond in the same chat window. They will show you how you can chat live as an online expert, “push pages” to visitors and so on. At the very least, this demo is quite interesting if you’re trying it for the first time.

Michelle, our online manager, will be online at GlobeAlive.com to give visiting experts demonstrations anytime from 10am to 10pm Pacific time, starting tomorrow, Monday, September 24th and going strong all week. She is also a top expert at askme.com and would be glad to chat about her experience with you.

We already have a long list of top askme.com experts who tried the demo and are now joining us for the beta-test. We hope you join us too.

Thanks for your time… and we hope to see you online,

Founders
www.GlobeAlive.com

Answer : Thanks for the invites... I will stop by and check it out soon.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 6568961
Asker : musicmkr84
Subject : Electromagnetic Waves
Private : No

Question : My astronomy teacher gave me this question....

How do you use electromagnetic waves on a daily basis? How are long-distance phone calls and cable TV transmitted in terms of electromagnetism?

Thanks for your time!
Allison

Answer : Well one way you use them is your eyesight! What we call "light" is just a slice of the full electromagnetic spectrum.

Long distance calls and cable TV (which actually originates from satellites) both use microwaves or other forms of EM to transmit signals back and forth to Earth.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 6609967
Asker : Anonymous
Subject : Nuclear fusion
Private : Yes

Question : How is fusion different from fission and where do on-going fusion reactions occur? Also, do you think the development of fusion as a nuclear source is worth the risks and what are some of the risks?

Answer : Fusion gets its energy from the same source as fission does, just in a cleaner (and better) way. Fusion is, of course, the fusing of light elements into heavier ones. Fission being the opposite splitting of larger elements into several lighter ones. The benefit to fusion is that the byproduct is not radioactive like in fission. Also the fuel for fusion, deuterium atoms (hydrogen with one neutron), is one of the most plentiful substances in the universe. The output of a fusion reaction (besides heat/energy) is helium.

In both cases the energy from the nuclear reaction comes from the mass differential that is present after the reaction. In both the case of fission and fusion there is less mass-per-nucleon after the reaction that before.

On-going fusion reactions are what power our sun. Each second it converts about 700,000,000 tons of hydrogen into around 695,000,000 tons of helium.

Fusion as an energy source would be nothing less than one of the largest achievements of mankind. Clean, limitless energy would literally be the result!

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Please refrain from asking questions as private unless you really need it to be. No one else can now read this interaction, which limits its usefulness.
Rating : 5

FUQuestion : Paul,thanks a lot for exlaining fusion and fission. You really helped!

Answer : You're very welcome... I'm glad I could be of assistance to you.


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QAId : 6626069
Asker : chause@...
Subject : light years
Private : No

Question : how many light years is earth from the sun?

Answer : It's not anywhere close to even 1 light-year from us. It's only 93 million miles away. The light leaving the sun travels only 8 minutes (far short of the year required for it to be one light-year away) before striking the Earth. So if you want to know how much of one light-year it is away, find the number of minutes in a full year, and then calculate what fraction 8 minutes is of that.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Answer : Don't forget to rate the answers you've received.

Thanks,
Paul Doherty


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QAId : 6645905
Asker : prenaud
Subject : physics
Private : No

Question : If plane A flying at an altitude of a 1000ft drops a 100# bag and plane B flying at an altitude of 2000ft also drops a 100# bag, will the speed of the bag from plane B on arrival on the ground be twice as fast as the one from plane A?

Answer : Both bags are identical in weight (and presumably shape) - they will be travelling the same speed when they strike the ground.

Why? Because of a thing called terminal velocity. Terminal velocity is the fastest unaided speed an object can fall in air, and is determined by the object's shape (surface area) and weight. Once an object has accelerated to a speed where the air resistance it encounters is equal to it's weight at that altitude it will no longer go any faster.

Both bags will accelerate from gravity at the same rate. While the second bag falls longer than the first, both will have reached terminal velocity long before hitting the ground, thus they will be travelling at the same speed.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 6661171
Asker : Anonymous
Subject : earth, moon, and gravity
Private : No

Question : Objects fall because they are attracted to the gravitational force of the Earth. This same force also keeps the moon in orbit.

Does this mean that the moon is "falling" towards Earth? What keeps that distance between the Earth and moon?

Answer : Yes it is "falling" towards the Earth, in exactly the same way as a satellite or the space shuttle in orbit fall around the Earth. Gravity doesn't stop just because you are at a distance from the Earth, it's just lessened in force. To "fall around" the Earth at whatever distance you happen to be, you must traverse a *horizontal distance* each unit of time that is enough to maintain your distance from the surface of the Earth. Since the Earth is curved, when you travel horizontally you are essentially moving *away* from the surface of the Earth. When the distance you gain away from the Earth by your horizontal motion equals the distance you fall towards the Earth in the same period you are in stable orbit.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Answer : Don't forget to rate the answers you've received.

Thanks,
Paul Doherty
Rating : 5


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QAId : 6682317
Asker : kristy_dx@...
Subject : gravity and the pendulum
Private : No

Question : 9.The Sears tower in Chicago is 443 m high.
(A)How long would it take a rock dropped from the top, to reach the ground?


Please show me how to solve this problem.

Thank You

Answer : You need to show an attempt to solve the problem before asking for help.

Here's what I did:

We know the formula for the distance an object has fallen is:

d = 1/2 (gt^2)

where d is distance we're looking for, g is 9.8m/sec gravitational constant, and t is the time in seconds the object has fallen.

We plug in our values:

443 = 1/2 (9.8 * t^2)

Multiply both sides by 2 to get rid of the "1/2" and we get:

886 = 9.8 * t^2

Divide both sides by 9.8 to get rid of our 9.8 on the right side and we end up with:

90.41 = t^2

Take the square root of both sides to get rid of the "^2" and we get:

t = 9.51

So the time the object fell was 9.51 seconds (if we can assume no air resistance).

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 6750755
Asker : Anonymous
Subject : launch/orbit /central forces questions
Private : No

Question : Hi I have some questions that I dont really understand how to answer, and I hope you can help me with any of them if not all of them!

1. a: Why are rockets usually launched in the Eastern direction? Which site has an advantage: Cape Canaeral (Florida) or Cosmodrome Baykonur (in Hazakhstan)?

b: Could a satellite be on an orbit which is not coplanar with teh center of the earth?

c: Does a rocket heat up more due to friction in teh air during the launch of when it falls back to earth?

2) Two satellites , A and B , are moving along the same circular orbit not far from each other. Satellite B which is behind A is attempting a docking with A by accelerating along the line AB. Is it possible to dock this way? (I said yes, cuz in due time the line AB will be tangent to the orbit , and point of tangency is where A and B collide or dock. However, I'm not sure this is right...)

Thanks for your time!

Answer : 1a)
I'm not sure about the Eastern launch - one reason could be that since the Earth rotates towards the East it keeps the ground station in visual contact with the rocket longer than if it went West. It may also be a momentum/rotational inertia thing in gaining speed.

1b)

I'd say no, if I understand what you mean by "coplanar" as related to a sphere. For it to be in orbit it has to encircle the Earth and would be traversing about it's middle no matter what direction it orbits in.

1c)

I would say there is more heat over less time in reentering the Earth's atmosphere than in takeoff, simply due to the speed involved. The amounts may be equal though since the takeoff takes longer. The heat shields weren't added for takeoff, you know. :-)

2)

If they're in the same orbit (meaning one is just "behind" the other distancewise) then yes I'd agree they can dock that way.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities




Rating : 5


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QAId : 6766543
Asker : Anonymous
Subject : mass
Private : No

Question : Hi :-)

Why does matter have mass?

Why does matter take up space?

Mark

Answer : Matter and mass are basically synonyms of each other. They mean the same thing.

Matter (mass) takes up space because that is part of it's definition. It is composed of material (atoms) which themselves take up space, so the result of making something from them must also take up space.

http://dept.physics.upenn.edu/courses/gladney/mathphys/subsubsection1_1_3_1.html

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 4


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QAId : 6770459
Asker : Anonymous
Subject : e=mc2
Private : No

Question : dear expert,

Could you please (in simple terms) explain to me what Einstein's most famous equation (e=mc2) actually means, and how it is being used, both in the past and present.

Thanks

Answer : The equation is an "energy-mass equivalence", connecting energy and mass in ways that were not thought of before Einstein. It literally means that mass is congealed energy, and shows the amount of energy contained in an object.

It was this showing that mass is energy that led to the atomic bomb and atomic energy, as well as nuclear medicine. Hopefully fusion power will be coming before much longer, which will give us nearly limitless clean power.

Please ask a follow-up if you need more information.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 6780030
Asker : Anonymous
Subject : heat conducting electricity
Private : No

Question : Most metals conduct heat & electricity. Do all things that conduct heat also conduct electricity?

Answer : Interesting question. I would say yes, since the term conductor applies to both electricity and heat, and all instances of either conductors that I can think of also conduct the other.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 6803091
Asker : Anonymous
Subject : North pole
Private : Yes

Question : True or false.
Impossible to get a cold in the north pole.
I don't understand this question for some reason. How could it be impossible but someone told me it was.

Answer : I don't see what they would have to do with each other - one is a location, the other is a sickness. Unless I heard something compelling from him I'd expect that not to be true.
Rating : 5

FUQuestion : I asked them why they said that and they should that the virus would be dead because of the tempurature up there. Is this possible?

Answer : Ah, an interesting angle. It looks like he may be right!

http://www.google.com/search?hl=en&q=%22catch+a+cold%22+%22north+pole%22


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

FUQuestion : Thanks for your answer. I am taking sexual education and well I wanted to do a weird topic. By knowing that some stuff dies at tempurates like sperm can not live in any tempurate besides 98.6 I thought but correct me if I am wrong. I was thinking how many people can not have babies in the North Pole due to the tempurate? However this topic may be to hard. Can you help me out a drop with even theory's. Thank you

Answer : Well sperm are kept outside the body to keep them below 98.6 as that is a tad too warm for them. I suppose in those environs they could be too cold and this would lead to fertility problems. Of course the scrotum has the ability to withdraw somewhat and rob the body of some heat when needed so this may not work unless you can convince yourself that people's bodies at the North Pole don't regulate themselves to maintain 98.6 degrees.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

FUQuestion : I just saw this in the newspaper.
FRANKFURT, Germany - Talk about keeping your cool under pres-
sure! Doctors at Giessen University near Frankfurt wanted to
prove men are more fertile if their crotch is kept cool, so
they have rigged up an air conditioning system for underpants.
The system works by clipping a battery-powered fan on to a
belt around the waist. This pumps air into tubes which lead
to the groin while nozzles direct the airflow. Straps attached
to the belt go around the legs like a climbing belt, keeping
the tubes and nozzles in place. "It works," says head re-
searcher Andreas Jung. "Not only is the amount of sperm
increased but it is faster-moving too. And that adds up to
more chance of fathering a child."

So by going with this that means Alaska would have more babies instead of less right?
By the way thanks for helping me with this report. I wasn't going to do a topic like this till I heard from a friend about the North pole and colds.

Answer : Maybe more per populace. Alaska is very sparsely inhabited, compared to all other US states. The most populated city, which is I believe Anchorage, has only about 250,000 people. So while individuals may be more prone to foster offspring, the chances of meeting people to have offspring with may be less.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 6809410
Asker : alnebras31
Subject : physics
Private : Yes

Question : Can an object have an increasing velocity and a constant acceleration? Can the velocity of an object be zero at the same instant its acceleration is non zero?
thanks
regards

Answer : 1) Yes. Velocity is the speed and direction of motion. Constant acceleration could come from say a rocket ship engine which is not not turning the ship, but is increasing it's speed.

2) Yes. Witness a ball thrown up into the air. From the time you throw it upward it is being accelerated downward by gravity constantly (thus it is always under acceleration) yet at the peak of it's throw/trip downward it is momentarily "at rest" yet still under acceleration. So any acceleration that is opposite to current motion can result in this effect when the object is "reversing itself".

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 6825025
Asker : blazerfan89@...
Subject : projectile motion
Private : Yes

Question : I am doing a project about math in tennis. I am trying to understand the physics and calculus involved in projectile motion and the parabolas involved in the ball's arc after being hit. I have found some sources but they are all very difficult to understand. Could you simply explain the equations with graphs. Also, what sources can you find that are simple and useful.

Thankyou,
Stephen M.

Answer : The best way to think of it is to seperate the horizontal and vetical components of motion. The vertical component is simply the result of the initial strike (angle and speed) followed by gravitational acceleration. The horizontal component is just the initial speed (if you neglect air resistance) given the ball when struke - that is, however fast the ball was travelling horizontally when it was hit is how fast horizontally it will be travelling when it hits the ground.

See this site for a visual demonstration and several examples:

http://www.physicsclassroom.com/mmedia/vectors/bds.html

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 6841031
Asker : Anonymous
Subject : SPEED OF LIGHT
Private : Yes

Question : How fast dies light take to get from the sun to the earth?

Answer : About 8 minutes.

FUQuestion : how was this solved? can you show the work of How fast does light take to get from the sun to the earth?

Answer : You just divide the distance (150,000,000 km) by the speed of light (300,000 km/sec) and you get roughly 8.5 minutes.

150,000,000 / 300,000 = 500 (seconds)

500 / 60 (seconds per minute) = 8.33 minutes

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities



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QAId : 6844469
Asker : vellad
Subject : Newton's third law
Private : No

Question : Can you clarify "every action has an equal and opposite reaction"? If this is true, how does a wall or the ground apply a reaction force when F=ma and a = 0 (for wall/ground) and how can you move anything if the object you're pushing is exerting the same force on you as you are on it? Also, if two balls of different mass collide, what forces are involved taking into account this law?

Answer : The forces are equal in any action/reaction pair. Whether there is a *resultant* movement of either object is a function of how much mass each object has.

As for being able to move an object and it pushing back on you. It's the very fact that the object "pushes" back on you (likely in the form of friction and inertia) that allows you to move it. Just think of it as anytime a force is applied an equal but opposite reaction takes place, but it can be in the form of simple resistance (like the floor or a chair that supports your weight).

See this site for some nice examples:

http://www.glenbrook.k12.il.us/gbssci/phys/Class/newtlaws/u2l4a.html

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5


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QAId : 6937685
Asker : Avon7
Subject : Heisenberg Uncertainty Principle
Private : No

Question : What would happen to Quantum theory if someone discovered a super small particle, or was able
to measure the position and velocity of a particle simultaneously another way?

Does our inability to measure something really qualify the advent of an entire branch of physics?

What happens to this branch of physics once someone measures the position and velocity of an
electron simultaneously without disrupting it?

regards,

Julian

Answer : Well your supposition is based on the concept that it's even *possible*, which in my opinion, it is not. I'd say that quantum mechanics is a response to the idea that not all systems in nature will be approachable from the classical viewpoint. And that to make further progress with such random systems (quasi or otherwise) it was necessary to move to something like it.

If you have some ideas of how you can obtain the position and momentum of a sub-atomic particle in some way other than showering it with electromagnetic radiation of some flavor I'd like to hear about it, as it would prove extremely interesting.

As you state though, if someone does come up with such a way, however unlikely that is, it would have a profound effect on quantum physics, but not as profound as you think I expect. It has become entrenched as a tool and would not be dealt a killing blow by such a discovery I feel.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities




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QAId : 6937724
Asker : Avon7
Subject : Heisenberg Uncertainty Principle
Private : No

Question : What would happen to Quantum theory if someone discovered a super small particle, or was able
to measure the position and velocity of a particle simultaneously another way?

Does our inability to measure something really qualify the advent of an entire branch of physics?

What happens to this branch of physics once someone measures the position and velocity of an
electron simultaneously without disrupting it?

regards,

Julian

Answer : Well your supposition is based on the concept that it's even *possible*, which in my opinion, it is not. I'd say that quantum mechanics is a response to the idea that not all systems in nature will be approachable from the classical viewpoint. And that to make further progress with such random systems (quasi or otherwise) it was necessary to move to something like it.

If you have some ideas of how you can obtain the position and momentum of a sub-atomic particle in some way other than showering it with electromagnetic radiation of some flavor I'd like to hear about it, as it would prove extremely interesting.

As you state though, if someone does come up with such a way, however unlikely that is, it would have a profound effect on quantum physics, but not as profound as you think I expect. It has become entrenched as a tool and would not be dealt a killing blow by such a discovery I feel.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

FUQuestion : Hello Paul,

Actually I do have an idea on how it MIGHT work. One way in which we could thoerically measure an atom's position and velocity at the same time is by using neutrinos. Since they contain NO MASS whatsoever they may be able to pull it off. Hence, Heisenberg Uncertainty Principle will never be broken, just modified when it comes to neutrinos or something very like it.

How's that?

regards,

Julian

Answer : Sounds good, but are you *sure* they have no mass?

http://www.google.com/search?q=neutrinos+mass

And even if they didn't light (ER) doesn't either (rest-mass anyway) and yet it imparts energy to the electron - a primary tenet of HUP.

FUQuestion : Hi.

Thanks for the website. It was very informative. Well, it appears that neutrinos do have mass but here's my next question.


Is there something that contains NO MASS whatsoever that could theorically measure an
atom's position and velocity at the same time? Thanks! :)

regards,

Julian

Answer : Not that I'm aware of - and it's not mass per se that causes the Heisenberg effect (I'll call it) - it's energy of any sort. The type of rest-massless light we use to view an electron imparts too much *energy*, not mass, which sends the electron off in an unknown direction (or when using longer-wavelength radiation to avoid the velocity change and instead can no longer pinpoint the location with any degree of accuracy).

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

Rating : 5

FUQuestion : You mentioned that any kind of energy causes the Heiseberg effect.

But what if we use something that had NO ENERGY of any kind? Would it possible to know both the velocity and position at the same time then?

best regards,

Julian

Answer : You're the one trying to buck the staus quo, here. :-) I'm still of the mind that it's not possible to know both these things simultaneously, and I can't conceive of how nothing (massless, energyless) can be used to ascertain the information we need. Whatever we use to view the object must, by definition, interact with the object. Unless we can "sense" the presence and info we need without touching it I don't see how it's possible.


--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

FUQuestion : Hi Paul! :)

I'm curious about your comment, "Whatever we use to view the object must, by definition, interact with the object. Unless we can "sense" the presence and info we need without touching it I don't see how it's possible."


What did you mean by "sense"?

regards,

Julian



Answer : "sense", meaning "gather information about the whereabouts or positional/directional information". I used the term to describe the method required to detect this information in the absence of matter or energy.

--
Paul Doherty
http://members.home.net/iqueue
DOS/Windows Utilities

FUQuestion : How can this method be able to detect information without matter and energy?

Julian

Answer : I was saying that *unless* we found a way to detect it without matter/energy that it was not possible. I agree it's impossible; that's what I was saying.

My webpage has been changed, to protect the innocent... ;-)

--
Paul Doherty
http://home.attbi.com/~iqueue
DOS/Windows Utilities



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QAId : 6940294
Asker : neil_a_clarke@...
Subject : speed, distance, time
Private : Yes

Question : I need help on how to work out speed, distance & time calculations without the use of a calculator.
I am from the UK, and I will be doing aptitude tests for entry into the Royal Air Force as a pilot, and one of those tests is SDT calculations in your head. I am OK with relatively basic questions, but tend to struggle with tougher ones.
I was just wondering if there was a simple way to work these out in your head?

Kindest Regards.

Need More Information : Can you give some examples that you consider easy and some that you consider hard?

FUQuestion : Basically, is there a simple way to remember how to perform mental SDT calculations?

Easy: Car travelling at 30mph. Leaves a destination at 12:30hrs, and travels for 120 miles. What time will the car arrive at its finish point?

Answer: 16:30hrs (I hope!)

That is about as far as it goes. And all my answers have to be worked out in my head, without the use of a calculator.....

Answer : I'm sorry but I don't really know a way to shorten those - I just divide the speed (30) into the distance (120) to get 4 hours.
Rating : 1


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QAId : 6960636
Asker : Avon7
Subject : Quantum Entanglement
Private : No

Question : Hello agagin Paul!

Can you explain how quantum entanglement works?

regards,

Julian

Answer : If I knew how it *works* I'd be in line for a Nobel prize this year. ;-) What it is, is the effect whereby particles remain "connected" even when separated by extremely large distances. Measuring one (for spin, for instance) instantaneously, and at speeds far greater than that of light, causes the paired particle to assume the opposite spin. Very odd stuff.

More info here:

http://www.techrepublic.com/article.jhtml?id=r00220011203ern01.htm&fromtm=e102-3

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

FUQuestion : I was unable to get into the website that you gave me, however, I checked another source and found it most interesting. It appears that this technology holds great promise for quantum computers. Given that our computer technology continues to accelerate at an alarming rate, how soon do you think we will have quantum computers available to the public?

regards,

Julian

Answer : I can't really predict as I'm not up on them - but from the accounts I'm seeing we can expect experimental versions within 10 years.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

Rating : 5

FUQuestion : Hello again Paul!

I was curious by your comment regarding quantum entanglement,

"What it is, is the effect whereby particles remain "connected" even when separated by extremely large distances. Measuring one (for spin, for instance) instantaneously, and at speeds far greater than that of light, causes the paired particle to assume the opposite spin. Very odd stuff."


Does this mean that we could theorically reassemble a chair with the aid of quantum entanglements?

regards,

Julian


Answer : An interesting proposition. But this only works for particle pairs to my knowledge, so a chair wouldn't really have an associated pair that could be linked in this way. If you could find a way to *represent* the dimensions of a chair you might be able to communicate that information to a remote site by way of entanglements.

FUQuestion : But would this chair be a replica?

regards,

Julian

Answer : Assuming the hurdles above were remedied I suppose so - it would be a copy of the original chair. Remember this is an inanimate object. And that we're also assuming we can somehow form wood from this input in some way.

FUQuestion : What about using folding space as a means of teleporting macroscopic objects?

regards,

Julian

Answer : I am not up on that as a potential means of moving physical objects, sorry.

FUQuestion : Hi Paul,

You know, I just came up with a crazy idea on overcoming the HUP. The idea is to somehow use an outside force to freeze the atoms in a certain
position by a warping effect. Or to compress them all together so strongly that they can't be altered in their course by the bombarding photons.

What do you think?

regards,

Julian

Answer : If you did either of those things to avoid HUP you have already violated it in a different way - you've altered the very thing you intended to measure before you even try to measure it. And I'm not sure you could compress them anyway since atoms aren't small enough to be the boundary condition for HUP - smaller sub-atomic particles like electrons are.

FUQuestion : Okay, this will be my last attempt at HUP and if this doesn't sound theorically possible, then I will graciously admit defeat. :) If we use larger photons we could measure the position and velocity at the same time because they have less momentum, but the problem is that the image of the molecule or
atom that we want to see will be blurry.


1)But what if we could construct an “eyeglass” or “contact lens” that could correct the
blurriness of the large photon, thereby allowing us to see and measure the velocity and
position at the same time?


Or


How about this....


In order to see an atom or molecule precisely, we must use small photons. The problem with these small photons is that they have a much greater energy packet.


2)But what if we could contruct a device that would reduce the energy of the small photon and use those "contect lens" to correct the bluriness? Would it be possible to measure the molecule's position and velocity at the same
time then?

regards,

Julian



Answer : it's not a question of large or small - it's a matter of frequency. Take light indoors vs outdoors for a moment. You can sit indoors and be bathed in incandescent light all day without a problem, right? But step outdoors on a sunny day and in two hours you'll be burned. Why is that? Because the sun's light contains high-frequency light like ultraviolet (above blue and violet in frequency and outside the visible range) that damages your skin due to its potent energy content. The same is true of the energy levels of the photons of "light" (not visible but the same phenomenon) that we use to view these small objects. Use too high a frequency (with its correspondingly small wavelength which is what allows us to see such fine details) and you will blast the object you're viewing with enough energy to ensure you'll know nothing about it's direction of travel. Lower the frequency to where the energy imparted is little enough to not send the object into orbit and now your wavelength has lengthened to the point where you lack the precision to pinpoint the location. It's not a matter of focusing to get the information - your "light source" lacks the fidelity to give you any detail to *focus on*. You can't bring into focus what isn't there to begin with.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

FUQuestion : Hi Paul,

So basically what you're saying is that it is not possible with the aid of advance technology to change the frequency because the light source is inherently out of focus.

1)Correct?

2)Will this always be the case, no matter how much we advance in our technology?

regards,

Julian

Answer : It's not "out of focus" - the light source is not granular enough to show any details. You've still got your head in the macroscopic world. You've got to realize that the reason you can see with as much detail as you do is because the wavelength of light our eyes use is much smaller than the smallest details we attempt to see. For instance a basketball is far larger than the wavelength of light we use to view it with (thus it can cast a shadow and reflect the light that strikes it). Even the pits in the basketball or the smallest details are huge compared to the wavelength of light we use to see it with. But with an object as tiny as an electron we can barely generate radiation with wavelengths that small - and when we do it's of huge energy - do you see that you can't render any of the details of an object that is significantly smaller than the wavelength of the light you illuminate it with? It's like a cattail sticking out of the water in a lake. If you throw a stone out in the water and make a wave, that wave will pass the cattail's stalk and be unmodified by it - the wavelength of the wave is too large to "see" the cattail stalk (and is not reflected or impacted by it). That's what it's like to attempt to see an electron with longer-wavelength light. And is why we must crank up the frequency to see them (and brings us to our "too much energy sends the electron into orbit" problem).

Remember that:

speed of light = frequency * wavelength

and that the higher the frequency, the lower (shorter) the wavelength

F*w = speed of light (big frequency (i.e. fast oscillation) times small wavelength)
f*W = speed of light (small frequency times long wavelength (covers more ground in each oscillation)

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

FUQuestion : Hi Paul,

If the HUP is here to stay for good, does this mean that the universe is probablistic and not deterministic?

regards,

Julian

Answer : Perhaps - or maybe we can't fathom the method fo determinism in play as of yet (or perhaps ever).

FUQuestion : I received a response from another expert and here is a direct quote:

"I never really agreed with that large photon/small energy thing. It is somewhat true because the smaller the energy, the less condensed the photons would be. There IS a way to "focus" the energy of smaller photons. Using a lens for larger photons would still not exactly work. Although you could focus it some, you could never focus it more than the sensitivity of the photons themselves. Its like a dot matrix printer. Although the dots are big, and when bundled together, make a nice picture, you cannot become any clearer than the size of the dots. Inkjets and printers that use smaller dots get more detail because they can focus on smaller things. You can take a low-energy photon, and using some form of gravity lens, focus it into a smaller photon, or actually, a more condensed photon. This would eliminate the heisenburg uncertainty principle, except for one thing. The low energy required can not be detected as of yet with convetional detecting methods. Until we can detect lower energy photons more accurately, we are stuck with hup."

Any thoughts?

regards,

Julian

Answer : I've never heard the concept he speaks of where a photon has a particular "size" - the only thing size-related in the phenomena of light that I can think of is the wavelength, and that's more an issue of resolution. How do you size a quanta of pure energy? It has no mass - how can it have size? His analogy of the dots in a dot matrix printer is quite similar to mine above; he too is attempting to show you that you can't see more clearly than the wavelength of light you use to see something with.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

FUQuestion : Hi Paul,


A thought just occurred to me regarding the theorical technology of the transporter in Star Trek. Thanks to the HUP, the technology will never become a reality, but it also cannot be plausible even if we accept the premise of the show and I'll tell you why. Whenever you see crew members beaming onto the surface of a planet, the environment is usually pleasant and sunny. Once the crew members have arrived, their atoms wouldn't be able to reassemble due to the Sun's rays. Since the sun also contains photons, they would cause a major disturbance on the crew members atoms, hence, there would be no way to put them back together anyway.

What do you think?

regards,

Julian

Answer : I suppose you could assume some shielding could occupy the space where the person was to be beamed to, temporarily protecting the void where the body will be reconstructed.

FUQuestion : Yes, I've thought of that too and for a moment I was considering forcefields but they wouldn't work because they are made of photons, so that means more disturbance and more headaches! LOL.

1)What do you think?


The only way I can envison it the Star Trek method would be to disassemble a person's atoms inside of a darkroom, very much like the ones photographers use in their studios to produce photographs. The darkroom would be the best alternative because it will keep all light, (including the Sun), as well as wind, and other disturbances out. So this sound more plausible. The problem with this concept is that right before the crew members beam down to the surface of a planet, they would first have to send down a shuttlecraft with a mini-darkroom on board and place it to the coordinates of the place of where they are about to teleport at. But that would really be impractical because it would take way too long. It would be easier just to send them by shuttlecraft anyway.

2)Any thoughts?

regards,

Julian

Answer : All that aside what makes you think that light will interfere with this theoretical teleportation? The light you refer to (indoor, sunlight filtered through atmosphere) do not contain the disruptive frequencies that relate to our discussion.

FUQuestion : If that's the case, what are the frequencies that disrupt the theorical teleportation technology?

regards,

Julian

Answer : If you're talking about disruption as it relates to the HUP frequencies we've been discussing it would be frequencies on the order of gamma radiation.

FUQuestion : But where would those gamma radiations be coming from?

regards,

Julian

Answer : Nowhere - that's why I said HUP wouldn't be interfering with your theoretical transporter.

FUQuestion : I received a response from another expert and here is a direct quote:

"Any physical material you make it out of, for example, will emit photons itself. Stars
aren't the only things that shine -- everything, including you, emits photons. Hotter things
will emit more visible photons, and relatively cooler things like my desk or my hand will
emit lower-energy photons (mostly in the infrared -- which is why they call infrared
"heat")."

That's very interesting. How do we emit photons?

regards,

Julian

Answer : You give off ER (Electromagnetic Radiation) in the form of low-frequency IR (InfraRed) from your body heat.

FUQuestion : So the fact that we too emit photons is what validates the HUP?

regards,

Julian

Answer : ? I'm not sure where you're getting these conclusions. "Photons" don't cause HUP - *high-energy* photons do. Infrared is a long wavelength (and low frequency) radiation that does have anything to do with HUP.

FUQuestion : But what purpose does infrared serve?


Answer : It doesn't serve a prupose - it's a by-product of our bodies being warm.


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QAId : 6992725
Asker : ecsec3
Subject : water balloons
Private : No

Question : my science project "How far can water balloon be tossed to someone before breaking?' In the 5th grade. I need some help getting the proceedures and Hypothesis started please. Thanks, Casey

Answer : Well I would start by defining the types of balloons to be used, and the degree to which they'll be filled (perhaps defined as "2 seconds of full water pressure from the faucet once situated"). Then I would define the procedures along the lines of how far the balloons will be thrown for their first trial, what constitutes a successful "catch" (i.e. does the catcher hold their hands absolutely still, or are they allowed to move their hands backwards as they catch, increasing the time of the impact, thus reducing the force over time (making the balloon less likely to burst). That may be over-engineering your problem - take what you need from that. Then you'll want to define how much of an increase in distance there will be from trial to trial, and how the results will be tabulated. I'd suggest you run at least 4 trials and average the breaking distances.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

Rating : 5

FUQuestion : Thanks!!!!! Casey

Answer : No additional info required.

You're welcome!


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QAId : 7008559
Asker : oscard1
Subject : Hexadecimal number system
Private : No

Question : How many characters are required to represent the value of one million for a hexadecimal number system?

Answer : 5 characters

Decimal 1000000 = Hex F4240
Rating : 5


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QAId : 7032488
Asker : Anonymous
Subject : collision ( experiment)
Private : No

Question : 1- how is the force felt during a collision related to the duration of the collision ?
2-why is it desirable to have the same initial speed for each data run ?(in collision experiment)
3-what are possible reasons why the change in momentum is different from measured impulse?(in the collision experiment)
I have used in the lab the pasco system to do this experiment :
the cart hit sensor and the computer give me the result but I couldn't explain the graph they are the same graph that I have seen for the implus and momentum in any books but I want to understand them thus I asked you the above questions.

Answer : The force is the same in a collision regardless of the duration of the impact I think you'll agree. However the force will do far less *damage* if distributed over a greater period of time. A perfect example of this would be if you jumped off a 10-foot building and landed on a beach (sand), and then jumped off the same building onto concrete. The force is the same but the time over which the force was applied is dramatically different.

You want the same initial speed likely for the same reason you always want consistency in an experiment - without keeping those variables you're NOT testing constant how can you ever say that the variable you are testing was the differentiator?

I don't have the graph you refer to, so I'm not sure what you're asking with that last one. I'm guessing from your description that time of impact may be a factor here as well?

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities



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QAId : 7051943
Asker : bina_andheri@...
Subject : physics
Private : No

Question : please explain the concept of relative velocity.

Answer : Relative velocity would relate to the idea that a measurement of one object's motion is always taken from another frame of reference that is also in motion. So the measured velocity is seen as the difference between the measuring frame's motion and the object being measured. As an example if you were to measure the velocity of a receding star you would be measuring it's velocity relative to your own - the Earth's rotation and orbit around the Sun are two major factors contributing to your own motion.


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QAId : 7079598
Asker : Anonymous
Subject : Happy New Year
Private : Yes

Question : I wish all a Happy New Year. Now lets get onto the questions. I read once waves like light don't need a medium, however I read many scientists thought ether wind can change the direction of light. Does that wind change the medium? If so that proves that light travels somewhat in it's own medium or makes it's own. Also I read a review about a movie and it said something about Einstein's mysterious missing waves. What are they talking about? I know only drops about Einstein and I want to learn more. I knew he had problems at math at the beginning before he taught him self math. Then he was a master at it. I know well the basic's. Thank you for your help. If you don't mind can you send me a link about his life. I read the information in Encarta but that makes me wonder more. Thanks again

Answer : Light doesn't require a medium. But it does get impacted by one (air, water, etc). Light travels its quickest in a vacuum. In a medium such as air or water there is an absorbtion and reemission process whereby the photon that emerges out the other side is a "new" photon, and not the original one that entered. This process makes the effective speed of light through these mediums less than its speed unfettered in a vacuum. Light's speed through air is about 99% of its speed in a vacuum, while through water is about 75% of the speed in a vacuum.

Wind does not change the speed of light, but temperatures (and therefore density) of air do. The "mirage" is a common phenomena that is even seen on highways. This will appear as a "wet area" on a dry highway off in the distance near the horizon. What is happening there is that the heated pavement warms the air immediately over it. The light that leaves the sky just at the horizon and is angled down slightly (so it should strike the pavement) is deflected as the part of the wavefront closest to the ground is less impeded by the less-dense hot air near the ground, with the result that the light "bends" from its straight line path. The result for you the driver since you interpret light as a straigh-line event is that you see part of the sky from the horizon as being on the road surface, which gives it that shimmery appearance.

For Einstein info this looks like a good place to start:

http://www.westegg.com/einstein/

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities



Rating : 5


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QAId : 7101180
Asker : crj14
Subject : physics
Private : No

Question : So far I have completed physic experiments on reaction time, momentum and acceleration. So.... I'm writing to ask if you know of any other experiments in which I can do on a high school level.
Thank you



Answer : Here is a good site with a lot of ideas for projects:

http://www.glenbrook.k12.il.us/gbssci/phys/phys.html

"Project Corner" of the same site:

http://www.glenbrook.k12.il.us/gbssci/phys/projects/proj.html

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

Rating : 5


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QAId : 7144687
Asker : laurali
Subject : lenny an bobby
Private : Yes

Question : hi my name is melissa
i am 13 years old and i hve thi kind of problem and i was woundering if you could help me out. ell the problem is i like thi kid lenny and he liked me but i dont know i he like me or is goin to ask me out. now the other prolem is that i like bobby and i ont think he likes me but in away it seems like he dose. i want to go out with him but he is always mean to me i dont understand well please email me back with these answers and thank alot

Answer : I think you meant to ask the question in the "psychics" category, not the "physics" category. But as long as I've got you here:

1) Don't waste your time waiting for people who treat you badly to figure out that you're actually worthy to be nice to - they are not worth your trouble. And, much to your surprise, when you stop caring what they think about you is about when they start liking you anyway (not that this makes them any more desirable, mind you).

2) Put your faith in God, not psychics. They may or may not have a "gift" but faith in God and His Son is all you need to live a good life.

Best of luck to you,

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities



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QAId : 7157608
Asker : Anonymous
Subject : physics relate to daily life
Private : No

Question : my physics teacher once said that...physics is everything....

and i am working on a physics paper about it

I know that it is impossible to separate physics from us. Everything we do and happen around our life are all relate to physics.

but how can i express it more detail? and what kind example should i put in my paper to support it?

Answer : More detail would equal more examples. MOst desirably examples that show how closely coupled we are with the concepts of physics. The very fact that the person can hold the paper you wrote and use the light to read the words you wrote would be good examples. Also the fact that they are alive by virtue of a series of physics processes triggered by the presence of our sun and its resultant heat/radiation by way of yet another process (nuclear fusion). You can go on and on with these examples. Let me know if you need any specific ones.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

Rating : 5


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QAId : 7184490
Asker : patrick28657
Subject : humidity
Private : Yes

Question : Why exactly does high humidity make a hot day even more uncomfortable? Does it have something to do with the pressure it exerts on your body, maybe its the fact that you can't sweat as easily, could you help me out please.

Answer : It has to do with the fact that, even on a not terribly hot day, your body uses evaporation to cool it off. On a humid day, there is a higher relative humidity which means more of the air is water vapor - relative humidity is a measure of what percentage of water vapor is currently in the air as compared to the maximum amount that COULD be in the air at that temperature. When the relative humidity is high sweat that normally evaporates immediately (which cools your skin since evaporation is water going from a liquid (lower-energy state) to a gaseous (higher-energy state) form. That energy comes from your skin, cooling it in the process. When there is extra water vapor less will evaporate easily from your skin.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

P.S. Please do not ask questions of this sort as private. This is not a private question or of an embarrasing nature, and marking it private means no one can read and learn from our interaction.


Rating : 5


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QAId : 7214236
Asker : Anonymous
Subject : physics
Private : Yes

Question : Hi,
A car travels along a certain road at an average speed of 4km/h and returns along the same road at an average speed of 60 km/h. Calculate the average speed for the round trip.
I have tried several diff. approaches to this problem, and I am stumped! Any help would be greatly appreciated.
Thank you!

FUQuestion : I'm sorry I meant 40 km/h not 4 km/h.

Answer : Since the distance is the same in both directions you can just average the speeds.

(40 + 60) / 2 = 50 km/h

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

FUQuestion : Thats what I thought. But at the end of the problem the book says in (Don't say 50 km/h) as a hint!?

Answer : Hmmm - then I am stumped too.


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QAId : 7220370
Asker : jinghuawu28
Subject : what is mass.
Private : No

Question : what is mass

Answer : Mass is the material all objects are made from - basically it's what any material object is composed of.


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QAId : 7220401
Asker : Anonymous
Subject : torque
Private : No

Question : What is torque?

Answer : Torque is a twisting or turning force. When you use a wrench to turn a nut on a bicycle wheel, for example, you are creating a torque by way of the wrench. Notice that the farther away from the nut end of the wrench that you apply the force the more turning force is produced.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

FUQuestion : What is the unit for torque?

Answer : Usually pound-feet

http://www.dillonnews.com/convert.htm
Rating : 4.7
Rating : 4.7
Rating : 4.7


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QAId : 7220416
Asker : lovely_samy@...
Subject : help please
Private : No

Question : how does a lightning rod protect a house from lightning?

Answer : In addition to the other expert's answer a lightning rod *also* reduces the chance of a strike occurring in the first place. It does so by "bleeding" charge off the house, helping it maintain a neutral charge so as to be less likely to be targetted by a strike.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

Rating : 2


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QAId : 7224341
Asker : huge_angel
Subject : i need a website with unit conversion metric
Private : No

Question : i am looking for a web site
where they have all kind of unit conversion formula.
like feet to meter
meter to mile.
degree C to degree F

i really need formula.
thanks you

Answer : http://www.onlineconversion.com/



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QAId : 7226630
Asker : DrRicko
Subject : Speed of light and of electricity
Private : No

Question : This should be an easy one. Is the speed of electricity (as it's being conducted through a wire, let's say) the same as the speed of light or is it slower? (I assume, but perhaps I'm incorrect, that electricity in the form of lightning is equal to the speed of light).

Thanks for helping out with this one.

Answer : The resultant moving of "electricity" takes place at the speed of light (c) but the electrons that make up that charge/current move quite slowly. See these for reference:

Misconceptions of the "speed of electricity":

http://www.eskimo.com/~billb/miscon/speed.html


Less of an electrician's perspective:

http://www.jimloy.com/physics/electric.htm
End :


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QAId : 7234009
Asker : hvnlybls@...
Subject : wait (weight) problem
Private : Yes

Question : hi,

i would really appreciate if you answer this question. i always wonder
why is there a difference:

1. putting a 50 kg weight on somebody
2. letting a person(whose weight is 50 kg) stand on somebody

why is the weight felt by the person different?


i think i can't bear if a weight of 50 kg is put on my legs, but when my legs are paining & somebody stands on my legs - its quite bearable.

(i hope you've got my question. sorry for such bad expression)


thanx









Answer : If I understand your situation correctly I'd say the difference is in how the weight is distributed. A 50 kg weight will likely be much smaller and can be mounted anywhere. It also will not need much adjustment on the part of the wearer with regard to torques produced. A *person* weighing 50 kg, however, has arms and legs and their weight is not centrally-located as a weight is, so balancing them (rotational inertia and torques produced) makes them a more difficult load.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities



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QAId : 7269415
Asker : prankster888@...
Subject : Gravity in an equation
Private : No

Question :
If g=gravity in an equation, how do you express it as a number. What I mean is what is
g equal to? This may sound confusing to you....I'm asking for an equation like:
gravity=(weight of object)\(mass of object)
BUT ABOVE IS ONLY AN EXAMPLE. What is gravity equal to?

Answer : When 'g' is used in an equation it refers to the gravitational constant for the influence of gravity. It's value is 9.8m/sec^2 and does not vary with the weight of an object.


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QAId : 7269862
Asker : prankster888@...
Subject : Gravity
Private : No

Question :
The value of g(gravity) is 32 ft/s^2.
This means feet per second per second. Can you please explain to me what 'per second per second' means. When I think of second squared, I think of 1/60(of a minute) squared. As in:
If I skydiver was falling from 3500 feet it would take (3500*(1/60))= 58.3 seconds to reach the ground?

Answer : Acceleration is often called a "rate of a rate". This is because it is a measure of the rate of change in velocity (which is itself a rate of distance over time).

The formula for calcuating the distance of falling is:

d=1/2 gt^2

d = distance
g = gravitational constant (32 ft/sec or 9.8m/sec)
t = time in seconds of fall

So in the case of your skydiver we know the distance (3500) and 'g' so we need to find the time over which the fall took place.

3500 = 1/2 * 32 * t^2

3500 = 16 * t^2

3500/16 = t^2

218.75 = t^2

(take square root from both sides)

14.79 = t

So the skydiver has 14.79 seconds of freefall before striking the ground. Sounds about right, considering when I went skydiving I jumped from 14,000 feet and had about 60 seconds of freefall before having to open my chute at around 5,000 feet.

This answer neglects one important fact of this example. Namely that terminal velocity plays a role in skydiving, limiting the maximum speed of fall unaided through the air. Any person who falls for more than about 10 seconds has their further acceleration retarded and eventually halted by the air resistance they encounter. Thus no further acceleration takes place and they fall at that constant speed until something (the ground?) stops them.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities





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QAId : 7379414
Asker : ramot@...
Subject : Interesting question about the stars - please help me solve it
Private : No

Question : At night - why is the sky black and all the stars are only dots of light? Why don't we see light everywhere instead of dots of lights in a black background?

An example of this: lets say you are wandering in a forest full of white trees. Anywhere you look you'll see white, right? That's exactly what is happening with the stars around us, so why don't wee see only white anywhere in the sky?

Answer : I expect it's because as vast as the numbers of stars are, the distances between them (and the empty space that results) is vast is comparison. Space is by far mostly empty.

If you think of the example of a flashlight - if it's close to you it's as you describe - you see light in a wide arc around the beam. It lights up things that not even in it's direct path. As you move it further away it's area of influence decreases to where only the actual point of the flashlight is seen and nothing near you is illuminated by it. Also remember that when the flashlight was near part of the reason the it can illuminate things near it without them being in a direct line is because of all the other "things" around - you, the ground, walls, etc all help to reflect a lot of the light back and to provide ambient light. In space we have no such materials to provide for this reflected ambient light.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities



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QAId : 7384002
Asker : lil_lit
Subject : pendulum
Private : No

Question : hi,
i)A pendulum tied to the ceiling of a train will swing to the left if the train accelerates to the right. Why is that so?


Answer : Because the pendulum, like you if you were in the train when it began it's acceleration (also known as a "turn") to the right, tend to travel in a straight line unless an outside force tries to change your path (inertia). The train is turning while the pendulum continues with it's forward momentum (until pulled into line by it's suspension string). The same thing happens to you in a car that turns. The car begins a turn, using it's tires and suspension to accomodate the change in velocity, and you the passenger either provide the same force by bracing against the inside of the car, or your seatbelt provides the force for you.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

FUQuestion : Let's say the train accelerates forward, the pendulum will swing backwards. Just like me in the car, if the car accelerates forward, i will fall back onto my seat. Can I say that they're caused by the reaction force of the car and the train?...or is it just inertia alone? Another case is, let's say I slide a cup of water sideways(towards the right) on the table, I will see that the surface of the water is no more horizontal. The surface slants, where the left side is higher than the right side. What is the cause of it?..Could it be the reaction force ?

thanks

Answer : It's inertia. You're taking an object that's either at rest or in constant velocity, and changing it's velocity. The reaction is that it resists the change to it's velocity and that's why you see the reaction in the opposite direction of the acceleration applied.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

Rating : 4


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QAId : 7403532
Asker : SimonB
Subject : Colour
Private : No

Question : Greetings

Is there any reason why the bottom of the space shuttle is black and the top is white?

Many thanks

Simon B

Answer : The bottom is black because it's covered with a heat-resistant material. That material is what can withstand the tremendous heat that is caused by the friction of the ship as it passes back into our atmosphere. The air resistance and speed are so great that without that protective layer the ship would be burned to a crisp on re-entry. They ensure that the ship is oriented so that the bottom receives the brunt of the frictional forces.


Rating : 5


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QAId : 7403830
Asker : Anonymous
Subject : velocity
Private : No

Question : What forces would be acting on a car when it is travelling at constant velocity? What is the resultant of these forces equal to?
(this is part of a longer question which includes plotting a graph and describing the car's motion from it.)

Answer : Air resistance, thrust from the wheels on the road to maintain the constant speed, and friction of the tires on the road would the only ones I can see off-hand. The resultan of these forces is a net force of zero, since the car is in constant motion.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities



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QAId : 7407260
Asker : lisafortson@...
Subject : chemistry
Private : Yes

Question : A graduated cylinider contains 56 milliliters of water.A small rock is lowered into the water and the water level rises to77 milliliters.The volume of the rock is?

Answer : Is this a trick question? It should just be the difference (in whatever units you need it). 21 milliliters.

The volume of the object should be equal to the volume of water it displaces (especially accurate for semi non-compressable objects like a rock).


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QAId : 7440824
Asker : Anonymous
Subject : physics
Private : Yes

Question : I need to know about Newton's three laws of motion and a example of each, if you could help me to better understand.



Answer : http://www.aloha.com/~isaac/3laws/3laws.htm

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities



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QAId : 7511145
Asker : Anonymous
Subject : Question of Force
Private : Yes

Question : I am trying to describe in basic terms a force equal to 5,000 Newtons. How can I explain this amount of force by using an everyday example that lay people like myself can understand?

Answer : A newton is about 1/5 of a pound. So a 100 pound person exerts about 500 newtons of downward force. Ten times that would be 5,000 newtons, or roughly the weight of ten 100-lb persons.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

FUQuestion : Thanks for your prompt reply. I'm looking for a description of Newtons that is a little more dynamic. How can I calculate the Newtons exerted if a 10 kg ball is dropped from a 10 meter height to a hard surface. Assume the ball comes to a stop in 0.25 seconds. If I'm on the wrong track please let me know.

Thanks,

Mark
Declined (Reason) : No reason was provided for declining this question.


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QAId : 7523096
Asker : Anonymous
Subject : Space Matters.
Private : No

Question : Hello,

Is space a vacuum? I mean are there any atoms (other than stars and planets and meteorites, etc) in space?

Also, if I wanted to breathe in something from deep into outer space, would anything go into my lungs?

Thank you for answering my questions!

Answer : There is very little in space, though it's not a complete vacuum. It's close enough to count though, as far as breathing is concerned.
Rating : 1


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QAId : 7638075
Asker : AstroConstant
Subject : EMF and PD
Private : Yes

Question : Can u pls tell me the major difference between emf and PD(Potential Differences)?
Also please tell me about good websites that contain info about this topic?
Thanks!

Answer : http://www.sciencejoywagon.com/physicszone/lesson/07elecst/potentil/epotenti.htm
Rating : 5


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QAId : 7696082
Asker : enoch87
Subject : Refraction
Private : Yes

Question : the ratio of the sine of the angle of incidence to the sine of the angle of refeaction is a constant. is this contant the refractive index (speed of light in medium 1 divided by speed of light in medium 2)?

what causes the light to disperse when passing through a prism?

will light disperse when passing through a rectangular glass box?

Answer : Not sure about your first question.

White light breaks into its constituent frequencies when passing through a prism because of what the change in medium (and the shape of the prism) does to the forefront of the light wave. To understand this picture the pointed side of the prism facing upward so that it looks like an upside-down "V". White light that is to pass through the prism we'll imagine is coming from the right and is coming directly horizontal (i.e. "flat") with respect to the vertical axis of the prism. Imagine at the forefront of the light a wavefront that is flat in the direction of the lights travel. As that light begins to strike the prism's angled surface (the right side of the upside down V) the bottom edge of that wavefront strikes the slower medium first. This slows that part of the wavefront down as it enters the slower glass medium, while the middle and top-half of the wavefront continue on at the faster speed, until they too strike the prism surface. In the end what happened is that the direction of the beam was changed. Now the light travels in a straight line through until the top-edge of the wavefront breaks out into the air first, thereby speeding up before the rest of the wavefront escapes the prism. So in the end the light has taken two hard left turns. As it turns out different frequencies of light that make up the white light "interact" more with the glass medium and get bent more or less by the glass of the prism. So by the time both hard lefts are made through the prism the spreading from this interaction has become more and more prevalent. This type of interaction through a medium is also what causes the sky to be blue. Blue and ultraviolet light interact more with the air in our atmosphere and get scattered more than the lower frequencies, which is where the blue color in the sky comes from.

Light will not spread in the same fashion through a rectangular box since you will reverse the spread of the initial entry from one side, on the other side when it exits (equal and opposite exit angle on the other side). The thing that makes a prism work is the fact it makes TWO left or right turns which increases the spread instead of cancelling it out.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

Rating : 4


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QAId : 7696964
Asker : swprequels
Subject : physics
Private : No

Question : for physics class, i need to build a rocket out of a 2-liter pop bottle...i know i need fins and a nose cone...what else do i need?

Answer : Propellant is all else I can see you'd need.
Rating : 5


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QAId : 7755568
Asker : nq68
Subject : Gravity
Private : No

Question : I am trying to understand how it is possible for someone to have set a new downhill skiing speed record that is considerably faster than the maximum speed that a skydiver can free fall at.
If a skydiver free falls, he accelerates to a maximum speed determined by gravity (assuming there is no air resistance). How is it possible for a skier to sky faster. What am I missing?

Answer : Many skydivers fall far faster than 140-200 MPH. Some speed skydivers reduce air resistance and can reach speeds in excess of 500 km/h (approx 300 MPH).


http://www.speedskydiving.net/info.php3
Rating : 4


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QAId : 7781864
Asker : shehnaz_khan
Subject : light(refraction)
Private : No

Question : " dear pauldoherty,
we all have noticed that when a cloth is soaked in water it appears a shade darker than its natural colour.
I know it happens because of refraction of light,but how does it happen can u please explain it clearly?"

Answer : http://www.mit.edu/~goodmanj/madsci/889017307.Ph.r.html

"Re: How does water change the apparent 'darkness' of many objects?
Date: Tue Mar 3 11:43:48 1998
Posted By: Jason Goodman, Graduate Student, Massachusetts Institute of Technology
Area of science: Physics
ID: 888004609.Ph
--------------------------------------------------------------------------------
Message:

This is a very good question; the reason it's taken me so long to answer is that I've been thinking about it for quite some time and discussing it with friends. I don't have a definite answer; all I can offer is a hypothesis.

Some observations: First, it's not just water that does this. A drop of oil on paper or clothing produces a similar effect. Second, it doesn't always make things darker. A wet spot on cloth or paper looks dark when you're on the same side of the cloth as the light source, but it looks lighter than the rest of the cloth when you look through the cloth toward the light. So liquids like water or oil seem to increase the transparency of porous materials like paper or cloth: they get easier to see through rather than actually darker.

One thing paper, cloth, soil, concrete, hair, etc. all have in common is that on a microscopic scale, they're partly transparent. Rock, sand and soil have lots of tiny, colored crystals in them. The fibers in hair, paper, and cloth look like transparent glass rods close-up. Most light-colored substances are actually composed of small clear bits: they look white because the light reflects off the surface of the clear bits, bouncing around like a billiard ball before scattering in all directions.

Things which aren't white, like colored sand, concrete, or hair, are often made of clear but colored substances, like a brown or green beer bottle. Notice that some light reflects off the surface of a beer bottle, but the light that gets through the surface gets colored because the glass absorbs some colors of light.

Light will reflect off a surface for one of two reasons: either the surface is a conducting metal, or the substance has a different "index of refraction". When light hits a conducting metal, it's as if it hit a brick wall: it has no choice but to turn around and go back. You can think of light travelling through materials with different indices of refraction as being like a crowd of people walking over sections of floor at different heights. When the crowd comes to the high "step" where a raised piece of floor begins, some of them cand climb up the step and keep going, while others decide it's not worth the effort and turn around to go back. Similarly, when light hits a material with a different index of refraction, some of it is reflected, some of it is transmitted.

Most solids, like rock, glass, hair, cellulose (cloth and paper), and plastic have a very high index of refraction. Air has a low index of refraction, so when light travelling through air hits a solid, lots of it is reflected (it's a very high "step up"). Liquids like water or oil have an index of refraction between air and most solids, so if you put a layer of water over a solid like glass or paper, you put a "halfway step" between the two "levels of floor". Just like a stairstep, this makes it much easier to go from one "level" to the other: more light goes through into the solid than when there was no water.

So you see that by providing an index of refraction between air and a solid substance, you reduce the amount of light reflected by the substance. If less light is reflected back into your eyes, the substance will appear darker. If the substance is between you and the light, more light will be transmitted through the substance to your eyes.

You can probably test this hypothesis. Look up the indices of refraction of various materials like glass, polyester, and cellulose. Look up the indices of refraction of various liquids like water, oil, alcohol, or glycerine. Wet the different solids with the different liquids, and see if the darkness of the wet spot changes with different liquids. Look in an optics textbook to find out how much reflection should occcur at the interface of objects with different indices of refraction, and see if your results make sense."
Rating : 3
End :


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QAId : 7849600
Asker : Anonymous
Subject : electric
Private : Yes

Question : Dear Pauldoherty,
Why all the tanker on lorries are cylinder in shape, but not rectangular or triangle?

PLease answer me as soon as possible.

Thank you.

Answer : A cylindrical shape applies the force (of say, sloshing liquid) equally in all directions and has no obvious weak point.
Rating : 5


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QAId : 7907774
Asker : Anonymous
Subject : Can people
Private : Yes

Question : Can people sit on the bottom of a pool without any help? Is this possible to break gavity?

Answer : That wouldn't "break" gravity. A person floats in water simply because the volume of water displaced by their bodies weighs more than they do. That is the only factor that determines whether something sinks or floats ("is bouyant") in water. For instance a brick sinks to the bottom of the pool but a styrofoam brick of the exact same dimensions doesn't. So whether you will sink or float (or somewhere in between) depends on how much fat or muscle you have. Very muscular people or those with very low body fat will sink in a pool.

FUQuestion : I agree, however my brother said he learned in Karate this can be done. It's almost like a monk's trick. Ever heard of this? I haven't, this is why I ask.

Answer : Without changing the volume or makeup of your body (say by taking only a shallow breath) I don't really see how you can modify this.

FUQuestion : So a tiny breath won't help? I just don't understand what he meant by this. Thanks. Maybe he is mistaken.

Answer : As I said a shallow (tiny) breath will make your volume smaller and increase your average mass (since part of your insides won't be relatively massless air). But other than modifying how much of a breath you take I don't see that anything else will modify whether you'll sink or float.
Rating : 4


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QAId : 7953726
Asker : Anonymous
Subject : Is the moon beneath our feet?
Private : Yes

Question : There is a song called The moon beneath her feet.

Could you please tell me if this title is accurate when people are on the moon? Do their feet touch the ground or do they fly?

Thank you

Answer : The moon only has about 1/6th the gravity of the Earth but yes you would be touching the ground.
Rating : 5


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QAId : 7971675
Asker : brownc66
Subject : Kinetic energy
Private : Yes

Question : Hi,
Can you tell me if kinetic energy is porportional to the velocity or the square of the velocity, or is it something else?

Answer : The square of its velocity:

http://www.physicsclassroom.com/Class/energy/u5l1c.html

"Kinetic Energy
Kinetic energy is the energy of motion. An object which has motion - whether it be vertical or horizontal motion - has kinetic energy. There are many forms of kinetic energy - vibrational (the energy due to vibrational motion), rotational (the energy due to rotational motion), and translational (the energy due to motion from one location to another). To keep matters simple, we will focus upon translational kinetic energy. The amount of translational kinetic energy (from here on, the phrase kinetic energy will refer to translational kinetic energy) which an object has depends upon two variables: the mass (m) of the object and the speed (v) of the object. The following equation is used to represent the kinetic energy (KE) of an object.


where m = mass of object

v = speed of object

This equation reveals that the kinetic energy of an object is directly proportional to the square of its speed. That means that for a twofold increase in speed, the kinetic energy will increase by a factor of four; for a threefold increase in speed, the kinetic energy will increase by a factor of nine" <SNIP>
Rating : 5


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QAId : 8001054
Asker : bjredwing@...
Subject : Sound Waves
Private : No

Question : Why do certain combinations of tones sound more pleasing to the ear than others?

Brian

Answer : I would say that at the simplest level some tones are harmincs of each other (one is a multiple of the other - like a note that is one octave higher than the same note of the octave below it will be twice its frequency). This simple relationship of each same-named note being twice the frequency of the one before it creates alternating constructively-interfering wave-fronts when heard which can be part of what makes them nice. Frequencies that are not related in any clear way deconstructively interfer and produce an audible beat pattern (heard best when two like instruments are just slightly out of tune with each other) and is highly irritating.

At the other end is the fact that human beings like order. Geometric shapes are pleasing because they suggest order and design. Music is pleasing to me for much the same reason. The flow of the instruments and the tensions and releases they make as they interchange in harmony suggest an underlying truth and an order to the universe.

Maybe that was more than you needed but I feel pretty strongly about music. Maybe you do too since you asked the question! :-)

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

Rating : 5


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QAId : 8045805
Asker : greenscorpio86
Subject : protons!
Private : Yes

Question : why don't the protons of an atom repel each other although they have the same charge?

Answer : Because they are repelled by the electric force, which acts across relatively large distances. A short-action force bonds nucleons (neutrons and protons) together in the nucleus of an atom and this force, while acting over a very limited distance, in large in force and overcomes the electrical replusion. This effect is the reason why nuclear fusion (the bonding together of nuclei from two or more atoms) requires such high temperatures (speeds) to overcome the electrical repulsion and bring them into close enough proximity that the nuclear bonding force can take over.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities



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QAId : 8051694
Asker : anusoniya@...
Subject : physics project
Private : Yes

Question : hi,
Could you send some project ideas based on gravity suitable for class IX students
thanks

Answer : The old experiment where an egg is to be dropped and students in pairs are asked to devise a method of slowing the fall enough to save the egg from a two-story or so drop, using limited materials is always a good one.

Here are more:
http://physics.bu.edu/py105/PhysFair/Projects.html


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QAId : 8054205
Asker : Anonymous
Subject : Didn't Einstein
Private : Yes

Question : Didn't Einstein love Germany even though they hated him? Thanks for your answer

Answer : Einstein was born a German, but he was also Jewish which could be what you're referring to when you say they hated him.

http://www.humboldt1.com/~gralsto/einstein/early.html

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

FUQuestion : So he didn't hate Germany?

Answer : You said Germany hated *him* not him hating Germany. With your reversed question it does appear Einstein took issue with his country of origin, Germany:

http://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=%22albert+einstein%22+hated+home+country+germany
Rating : 4


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QAId : 8126187
Asker : saliz
Subject : velocity
Private : No

Question : could if ever instant velocity be 0 and accelration not be 0? can i have an example?

Answer : No, because acceleration is a rate of change in velocity.
Rating : 4


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QAId : 8160530
Asker : Anonymous
Subject : ruler question
Private : No

Question : i have been trying to solve a problem for days but i have no idea. i tried looking everywhere for answers but got no luck. i hope you can help me. the problem says:

"hold a ruler horizontally balanced across your fingers. then try to move your fingers together so that both slide. it does not work. the ruler first slides over one finger and then over the other, but never both together. why is that?"

someone told me it might have something to do with friction but i'm not sure about that and i have no idea how it works. i would much appreciate any assistance and explanation.

Answer : I suspect it would have something to do with the rolling friction of the finger currently sliding not providing any resistance against which the movement of the other finger can be allowed to slip (since it's currently stationary and holding most of the weight - which is how you got the other to slip and begin sliding). Rolling (moving) friction is less than static (stationary) friction. A good example of this is a heavy box. If you push on it while it's stationary it can be hard to get it going, but once in motion the force required to keep it moving is significantly less. This also applies to tires on your car - that's why ABS is useful - it keeps the tires rolling so the friction forces are stationary (the tire relative to the ground, since it rolls as ground comes into contact with it) instead of the rolling friction that occurs when the tires lock and start to slide. When that occurs friction is greatly reduced.

I know a lot of that didn't directly address your question, but it seemed relevant material to cover. I hope some of it helps you.


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QAId : 8212569
Asker : mariyabaldwin@...
Subject : conversions
Private : Yes

Question : Hi PaulDoherty,
Would you, please, help me with the following?

A Porsche can accelerate at 12m/sec^2
What is this in km/hr^2?

So far I have: 12m/sec^2 * 1000km/m = 12000km/sec^2
and here I do not know how to convert sec^2 into hr^2?
Thank you so much for your help!!
Mariya

Answer : I think here you're going to be converting from meters to kilometers (by 1000, as you've shown above) and from seconds to hours which is the step you've yet to take. I think a division by 3600 would probably be what you're needing to convert from /sec to /hour
Rating : 4


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QAId : 8219260
Asker : jouellet001
Subject : angle projectile motion
Private : No

Question : Hello Pauldohery,

I was trying to play with projectile motion but ran into a little problem finding an formual that would work. I would be very greatful if you could help.

The problem is this: Finding the angle needed to get a projectile to land a sertain distance from a hight above ground (air resistance can be ignored).

Known:
(assuming normal cordintes Y0=0, Yground is negative, and moving foward is positive x)
hight at which is launched Y0
distance traveled in x direction
V0

I found something equations look like they might work in combination, but just leave me with a mess of cos and sin.

Truly Thanks,

Jeff


The numbers are not that important as long as the formual works for angles from above 0 and less then 90 degrees.

Answer : Try the forumula at the bottom of this page:

http://math.hope.edu/swanson/text/investigations.html

Remember that for the purposes of the vertical distance that you can simply use the normal gravitational constant to find how long before the object will strike the ground. Once you have that you can use the formula to find the range.


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QAId : 8220590
Asker : thirtykim@...
Subject : Jen again~~
Private : Yes

Question :
I really need your help.
This is relate to force and mass and mechanics

and I hope you could answer this question until thursday morning..




Q3> The tortoise and the hare had a rare over a distance of 3000 metres
whereas the tortoise plodded along steadily at 2.8m/s throughout the race,
the fast hare spent so much time showing off that he averaged only 1.4m/s for the
first 1000 metres of the race. At what uniform acceleration did the hare manage to cover
the remaining race, given that he beat the tortise by 2 seconds.

=============================================
And I tried this question
I did:

3000/2.8 = 1071.43 sec
1000/1.4 = 714.29 sec

then 1071.43-714.29=357 sec

2000m in 357 sec, starting v=1.4m/s

s=ut+1/2at^2
2000=(1.4*357)+(1/2*a*357^2)
2000=499.8+63724.5a
2000-499.8=63724.5a
1500.2=63724.5a
a=0.0235
and my final answer was a=0.0235 m sec^-2

Am I did correctly?


It's really urgent!!
and thanks for reading my questions..


Best regards
Jen






Answer : It seems righ to me, except wouldn't you want to remove the 2 seconds (since the hare wins by two seconds) from the part where you subtracted?

then 1071.43 - 714.29 = 357 sec

357 - 2 seconds hare will win by = 355 seconds

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

FUQuestion : then instead of substitute 357 I should put 355 right??

then the answer will be..

2000m in 357-2=355 sec, starting v=1.4m/s

s=ut+1/2at^2
2000=(1.4*355)+(1/2*a*355^2)
2000=499.8+63012.5a
2000-499.8=63012.5a
1500.2=63012.5a
a=0.02378
and my final answer was a=0.02378 m sec^-2


am i doing correctly??

Answer : Yes, I believe that would be correct.
Rating : 5


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QAId : 8222553
Asker : Anonymous
Subject : Distance & Speed: How long is the train?
Private : No

Question : Hello Mr. Doherty,
We were hoping you could assist us with the following math problem:

A train is going through a tunnel that is 650 feet long. The train enters the tunnel on one end. Twenty-six seconds later the last car exits the other end of the tunnel. The train is traveling 100 feet per second. How long is the train?

Is the algebraic formula for this problem:

100 = 650+x / 26

If not, would you be so kind as to explain the correct formula to us. In advance, thank you for your assistance with this problem.

Answer : It seems to me that if the train were zero length it would take exactly 6.5 seconds to traverse the 650-foot tunnel, right (100 feet/sec x 6.5 sec)?

So since it actually took 26 seconds till the last car cleared the end of the tunnel, the train would be:

(26 - 6.5) x 100

feet longer than a near-zero length train.

26 - 6.5 (= 19.5 seconds of additional travel)

19.5 + 100 (feet per second) = 1950 feet long for the train length.

I'm not sure what formula would be equivalent and would summarize what I just did. I don't think that way, usually, but I think the above is the right answer.
Rating : 3


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QAId : 8223262
Asker : sokolm86@...
Subject : acceleration
Private : No

Question : Hi PaulDoherty,

I am not quite sure how to solve the problem below. Could you take a look at it?

At the starting gun, a runner accelerates at 1.9m/s^2 for 2.2 sec. The runners acceleration is zero for the rest of the race. That is the speed of the runner at the end of the race?

So far I've got:

Speed = 1.9m/s^2 * 2.2 s = 4.2 m/s
However, I do not quite understand why it works that way. Is it possible for you to explain it to me? I'd really appreciate it!
Thanks a lot!!
Chris

Answer : I would agree you have the right answer. The velocity he is travelling is just the product of the acceleration and the time over which acceleration is applied. As in gravity, where we have 9.8m/sec^2, you can find the velocity by simply multiplying 9.8 times the number of second of fall. If instead you want to know *how far the object has fallen* you need to use the formula:

distance = 1/2 gt^2

So since the runner's velocity didn't change after his initial acceleration that means he is travelling the same speed at the end of the race as he was at the end of the 2.2s of acceleration at the beginning of the race. I hope this helped.
Rating : 5


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QAId : 8228073
Asker : swijegunar@...
Subject : mass
Private : Yes

Question : Does mass affect acceleration for a car rolling down an inclined plane? Why?

Answer : No, because an inclined plane is just an analogous situation to free fall. And free fall is not affected by mass (all objects fall at the same rate). More massive objects are attracted by the Earth in greater amounts, but by exactly the same amount such that it offsets their greater inertia from their larger mass.


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QAId : 8237827
Asker : domicile
Subject : Power
Private : No

Question : Hi,

If I see 120 V AC, 60 Hz, 0.3 A on a device, is that enough information to calculate the power in watts? If yes, what formula do you apply?

Thank you.


Answer : Yes:

Watts = Volts x Amps

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities

Rating : 5


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QAId : 8280077
Asker : Anonymous
Subject : help!<>speed of particle
Private : Yes

Question : Particle 1 is moving on the x-axis with an acceleration of 3.3 m/s^2 in the positive x direction.
Particle 2 is moving on the y-axis with an acceleration of 5.26 m/s^2 in the negative y direction. Both particles were at rest at the orgin at t=0s.
Find the speed of particle 1 with respect to particle 2 at 4.41 s.
Answer in units of m/s
Any comments of answrs need help visualizing on cordinate plane , help!
latter


Answer : Both particles are starting in the center at the origin, with particle A accelerating to the right, and particle B accelerating downwards. You will need to determe how far each of them will have travelled in the time given (4.41 seconds), which will be like any acceleration problem:

at^2 (where a is the acceleration, and t is the time)

This will give you the speed at 4.41 seconds if you plug in the acceleration for each particle.

As for comparing the speeds of the particles, I can't tell if he means the difference in their speeds (I suspect this is what is meant), or if he wants the relative speed of the two particles (which I'm not sure how to calculate).

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities



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QAId : 8307178
Asker : Anonymous
Subject : pleae help i need it !!!!! u wise sage
Private : No

Question : You are standing at the top of a cliff that has a stairstep configuration. There is a vertical drop of 13 m at your feet, then 11 m horizontal shelf, then another drop of 21 m to the bottom of the canyon, which has a horiaontal floor. You kick a rock giving it an inital horizontal velocity that barely clears the shelf below.
What inital horizontal velocity will be required to barely clear the edge of the shelf below you?Answer in units of m/s..
okay the anser to this question is 6.753346749 m/s

part 2:

How far from the bottom of the second cliff will the projectile land?answer in units of m
Let see if i can draw the pic:

[
[
[
13[
[
[______11____
[
[
[
[
21[
[
[
[
[


okay theres the pic now i am having problem with the math...this is what i did...This is where i am stuggling i need help!!!

y=1/2 gt^2 then solve for t so t=sqr2y/g......x=v*t(the time being the answer from 6.75334679 the anseer from the first part)

this is all i got but i dont even know what i am doing pleease help my on figureing this out
thanks...



Answer : I used only to two decimal places in all the work and here's what I did:

1 - You already determined the minimum horizonal velocity required to clear the shelf (6.75 m/s)

2 - Since we now know we're clearing the shelf the rest of the problem is just determining how far from the base of the cliff the rock will land.

So first thing we need to know is how long it takes the rock to hit the ground. This takes place in the same amount of time regardless of the horizontal component of motion so we can ignore it and calculate the time to fall as:

(total of 21 and 13 m sections = 34)

34 = 1/2 gt^2

(show the gravitational constant)

34 = 1/2 9.8 * t^2

(multiply 1/2 and 9.8 to get 4.9)

34 = 4.9 * t^2

(divide both sides by 4.9)

6.93 = t^2

(take the square root of both sides)

2.63 = t

So the time for the total fall is 2.63 seconds. And you already know the horizontal speed was 6.75 m/s. So now you just multiply that horizontal speed times the number of seconds of travel for the rock to drop and you have the distance from the base of the cliff:

6.75 (m/s) * 2.63 (seconds) = 17.75 meters from the base of the cliff.

--
Paul Doherty
http://home.attbi.com/~bitbucket911
DOS/Windows Utilities




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QAId : 8322471
Asker : maggiekill
Subject : Physics
Private : No

Question : Hello expert, could you please help me with some questions? Thank you very much!

Why polarised sound can't find in the nature?
Why do objects illuminated by moonlight lack colour but sun does not?
What is the casue of the red moon?

Answer : I'm not familiar with the concept of polarized sound.

Moonlight is too lacking in intensity to stimulate the cones of your eyes responsible for color vision, instead stimulating only the rods which are black/white vision.

The moon appears red only when near the horizon, for the same reason the sun tends towards that color near the horizon as well. Namely that the Earth's atmosphere scatters white light, diminishing the amount of high-frequencies (violet, blue, and some green) more than the lower frequencies (primarily red). By the time the moonlight has passed through this large amount of air (when the moon is at the horizon it's passing through the maximum amount of atmosphere) what you have left of the primaries is a lot of red with some green, which gives you the orange color you see.
Rating : 5


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QAId : 8327320
Asker : americanangel_11@...
Subject : Please help! She is not trying to cheat
Private : Yes

Question : You may help if you like even by sending this to my email addy. we have no idea seriously on how to figure the questions we sent you out. could you just even explain how. Or what we need to do. That is all we ask. I am her mother and have no idea how to help her in this area. do you have those questions still? It says on her homework that density = mass over volume. I guess what I am having problems with is what is mass and what is volume?
like on the board.? what do I do then divide? this is what I mean. I am a math stupid parent. please send your response to my email addy if you feel more comfy. we just moved from one state to another and the schools she is in now is way more advanced here. I have no idea how to do this. My address is ru_crazyman@yahoo.com . My name is Joy. This assignment is due tomorrow. Thanks for any help you can offer.

Need More Information : Please post the questions again as once I declined the previous I can no longer see the questions.

Answer : You also may get faster response by asking this question (with the questions you need help with, and your explanation above) to the general physics board where any number of us can answer it.
Rating : 5


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QAId : 8328516
Asker : Artem1s
Subject : Electromagnetism
Private : Yes

Question : Hi, I'm having problems with my physics investigation, the title of which is "What affects the strength of electromagnets and why". We are asked to back our findings with scientific theory but I cannot come up with any.

Thanks in advance for your help.

Answer : http://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=electromagnets&btnG=Google+Search


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QAId : 8331799
Asker : georgina_life@...
Subject : physics/time
Private : No

Question : Why is measuring time important?

Answer : Because humans like to mark the passage of events with some accuracy. And some processes and tools we use require relatively accurate measurement of time.


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QAId : 8336673
Asker : bparker_44@...
Subject : physics
Private : No

Question : My friend called me and asked me this, i havent done physics in a few years so i wanted to check it out.


if a plane traveling at 100 m/s dropped a package 50 meters from the ground, how far did it travel before hitting the ground?



thanks for the help
Brian Parker

Answer : Well you would use the gravitational formula for a falling object first to determin how long it takes the object to fall those 50 meters, which is in this form:

d = 1/2 gt^2

'd' is the distance, 'g' is the gravitational constant of acceleration (9.8 m/sec) and 't' is the time of the fall.

Since we already know the distance (50 meters) we plug in and calculate:

50 = 1/2 9.8 * t^2

(Combine the terms 1/2 and 9.8)

50 = 4.9 * t^2

(Divide both sides by 4.9)

10.20 = t^2

(Take the square root of both sides)

3.19 = t

So the time of the fall from 50 meters is 3.19 seconds. Now that we know the time to fall we simply multiply that number of seconds of fall by the horizontal component of speed (100 m/sec) to get:

3.19 * 100 m/sec = 319 meters of travel before hitting the ground.

--
Paul Doherty
http://ped.deadartists.com
DOS/Windows Utilities

Rating : 5


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QAId : 8348318
Asker : Anonymous
Subject : skier and hill
Private : No

Question : hi i've been stuck on this problem for days. i hope you can help me.

a skier swoops down a hill and over a ramp. she starts from rest at a height of 16 m, leaves the 9 m ramp at an angle of 45 degrees, and just clears a hedge on her way down, making an angle of 30 degrees with the vertical as she does. assuming that there is no friction, and that she is small compared to the dimensions of the problem, solve for H, the height of the hedge in meters.

answer in book: 2 m.

my book says this question was in the sir isaac newton contest (i don't know which year). i was wondering if you knew any website that shows detailed solutions to all SIN contest problems.

Answer : This site may help - it has solutions to this year's problems at the least.

http://www.science.uwaterloo.ca/physics/sin/sin.html



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QAId : 8352364
Asker : maggiekill
Subject : Physics
Private : No

Question : Hello expert, i have some questions which i don't understand! Could you please help me? Thanks a lot!

If a house is maintained at 25 degree by a heater with a thermostat and i wish to leave for an hour. Is it more efficient to turn the heater off while i'm gone ot leave the thermostat at 25 degree to maintain an even temperature?

What are the advantages and disadvantages of using neclear power and fossil fuels?

Answer : I would suggest that you would want to leave the thermostat at 25 degrees and on while you are away. Let's assume it runs 2 times during that hour for 5 minutes each time to maintain that temperature. If you had turned it off completely and returned in an hour it would perhaps have to run longer than 10 minutes to bring the temperature back up on your return.

nuclear advantages:
Uses small quantities of material to produce power
Little or no air pollution
Highly efficient method of power production

fossil advantages:
Fuel is plentiful (for now) and cheap
Easy to apply the technology anywhere in the world

nuclear disadvantages:
radioactive by-product after fissioning
fuel is difficult to produce
fuel must be secured as it could be made into a weapon if stolen

fossil disadvantages:
air pollution is tremendous
using a resource which is beginning to dwindle and may become scarce in the next few decades

--
Paul Doherty
http://ped.deadartists.com
DOS/Windows Utilities

Rating : 5

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