Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Adam Boutin on 07/02/2009 10:54:31
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Adam Boutin asked the Naked Scientists:
Hello I have a Science question.
Newton's Third Law of Motion states that for every action there is an equal and opposite reaction. According to that, when I stand on the ground and jump up, away from the Earth, then the Earth must also move an infinitesimal distance away from me.
Is this really true in practice?
I listen to your podcast (http://www.thenakedscientists.com/HTML/podcasts/) while I am doing my own science!
Adam
Boston, Massachusetts U.S.
What do you think?
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Adam Boutin asked the Naked Scientists:
Hello I have a Science question.
Newton's Third Law of Motion states that for every action there is an equal and opposite reaction. According to that, when I stand on the ground and jump up, away from the Earth, then the Earth must also move an infinitesimal distance away from me.
Is this really true in practice?
I listen to your podcast (http://www.thenakedscientists.com/HTML/podcasts/) while I am doing my own science!
Adam
Boston, Massachusetts U.S.
What do you think?
Yes, of course is true.
P.S. Please, stop jumping, I can't keep the book still in my desk! [:)]
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In practice, you'll just make a local deformation instead of making the entire Earth move.
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When you're 'jumping' you just force the Earth to 'hunt you down':)
Treat her like the lady she is, and stop jumping on her...
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But LeeE - but this doesn't mean that the Earth doesn't all move, albeit by a miniscule amount, surely?
Chris
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But LeeE - but this doesn't mean that the Earth doesn't all move, albeit by a miniscule amount, surely?
Chris
Umm... could you re-phrase that please?
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But LeeE - but this doesn't mean that the Earth doesn't all move, albeit by a miniscule amount, surely?
Chris
The Earth must move the same, because of momentum conservation law.
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The whole Earth doesn't need to move if just moving a small part of it will suffice. If you want to look at it as a rigid-body problem though, then the Earth moves away from you when you jump up in the air but then starts moving towards you, just as you start moving towards it, as you come down again. In this case, neither of you is stationary while you are in the air.
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The whole Earth doesn't need to move if just moving a small part of it will suffice. If you want to look at it as a rigid-body problem though, then the Earth moves away from you when you jump up in the air but then starts moving towards you, just as you start moving towards it, as you come down again. In this case, neither of you is stationary while you are in the air.
With "whole Earth" you mean "All the Planet with all its parts" or just "a part of it"? Because if you really mean the first, then you can simply say that its centre of mass moves, because of momentum conservation law; if then the centre of mass moves because of...that part moves that way...and the other part in that way...ecc., it's not my problem! [;)]
Do you know what I mean? You have to identify a point of the entire system which represents the system's position in space, and the simpler one is centre of mass.
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Hi guys; I get the feeling we are trying to separate the excretory wastes of the house fly from spilled grains of pepper. It is a difficult task [:)]
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LeeE, although you are right in that it leads to a observable elastic deformation oscillating in a bit and then back, some rudiment of it I would expect to travel the whole way through the Earth and back.
Does that mean that we will have oscillations in more phases than one?
One from where we loose our observational ability and then those coming back from what we can't measure?
If this is correct.
Head acheee
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You're forgetting about 'Noise'.
The deformation, as it propagated outwards, would soon be lost in the ambient noise caused by seismic, landslide, heating/contraction, road & rail traffic, wind, rain and insect activity.