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It is clear that if you push on some object, there is reaction of the same force. But is it the same energy? Thanks a lot.

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1 Answer 1

No. First of all, I'll take this version of Newton's third law changing force by energy:

Third law: When one body exerts a energy on a second body, the second body simultaneously exerts an enrgy equal in magnitude and opposite in direction to that of the first body.

You should see that it doesn't make sense to treat energy as a force, because it's not a vector.

But even if you talked about transference of energy, it wouldn't make sense. Think of a hot body heating a cold body. By your reasoning, the cold body would be heating the hot body too!

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This sounds like a friday afternoon beer debate :) The force reaction is a force of the same magnitude but opposite vector direction. But if You consider heat flow direction instead of a vector direction, a heated object responds with the same amount heat flowing in opposite direction i.e. the direction of heat flow from the perspective of first object is outwards, and the direction of heat flow from the perspective of the second object is inwards. Now it sounds legit :) –  Wojciech Feb 21 '14 at 16:13
There's no such thing as "Work direction" (there's a flow direction for heat but not for work in general) and there's no such thing as a third law for Energy. So Jinawee's answer is correct even if I agree its example may cause misconceptions. For Energy you have conservation of energy and that's all. –  DR10 Feb 21 '14 at 18:21
@Wojciech And things can get worse because Newton's third law is violated in much more cases than energy conservation. –  jinawee Feb 21 '14 at 18:26

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