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Physics/Gravity question.?

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I had to explain gravity to someone, and that actually got me thinking of something pretty interesting. We all know that gravity is the tendency of two objects with non-zero mass ...show more
Update : Bridget: Clearly you do not understand how gravity works. I explained ...show more
Update 2: Matt: You also seem to be oblivious to the mechanics of gravity, the ...show more
Update 3: Matt: Also, you have the wrong idea of that law. The law of equal and ...show more
Update 4: Before the next answer: Answer the question with a time, but make sure ...show more
Update 5: Kevin: It's funny how I literally just said "no other ...show more
Best AnswerAsker's Choice
Gravity would pull on the earth the same way every time the population jumoed, it would not gradually pull more with each succeeding jump. Each jump would be an independent action/reaction.

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Okay, nobody answered the question, so you all suck.

I chose you to spite Mr. Ooh big man Top Contributor.

Have fun with your points ;D
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  • Kevin M answered 2 years ago
    Before you go acting big and tall Matt is right, the net momentum is zero. You are misunderstanding what he means by that. Since you have assumed Earth is not moving around the sun or in relation to anything, its original momentum as well as yours is 0. By the law of conservation of momentum the net momentum will then always be zero.

    When you jump up, you will gain some momentum pointing up (obviously) and as you pushed off it, the earth will gain some momentum pointing down, equal to your momentum but opposite in direction. If that were the end of the story then yes, the earth would be moving but that's not the case. You soon find out that gravity will pull you back down, which will inevitably give you some downwards momentum. Again, the Earth feels the same, but opposite effect so it will eventually have some upward momentum equal and opposite to you. Then you will hit the ground in a perfectly inelastic collision and the ground will also hit you. The final momentum of the earth and of you will both be zero. Repeat until you have no energy to jump anymore.

    During your entire Jump, the net momentum of the system was 0 just as it began. The Earth will not have moved AT ALL.

    "force of gravity outweighs the force of momentum" First off momentum is not a force, it is a momentum. I think your point in that statement is the law of gravity outweighs the law of conservation of momentum, which is just wrong. The laws of physics work together, they don't "outweigh" each other. Also, nothing about momentum conservation implies that "when the Earth was forming, ever time a rock smashed into it, it bounced right back off". That would only be true if every collision was perfectly elastic, which none are.

    Source(s):

    ma brain
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  • Cool Hand Fence Sitter answered 2 years ago
    Forever, because the net momentum is zero and jumpimg will not alter this and change the position of the earth. (for every force there is an equal and opposite force)
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  • Physics/Gravity question.?
    I had to explain gravity to someone, and that actually got me thinking of something pretty interesting.

    We all know that gravity is the tendency of two objects with non-zero mass to accelerate towards each other, and that the greater mass an object has, the less it accelerates in comparison to other objects. Two Apples in zero gravity will "meet halfway", and the same is true for Earth and a falling object: Earth will move towards the object, but in such a minuscule amount it is virtually undetectable.

    So the question is: if everyone on the northern hemisphere of Earth jumped over and over again, how long would it take for a noticeable shift in Earth's position relative to it's original position, (i.e. for Earth to move in our direction enough to be noticeable via observation), considering the massive difference in mass between us and the Earth, and assuming that the Earth is not revolving around the sun, but is isolated from any other celestial body?
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