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How do action reaction force pairs arise?

by echolett
Tags: action, arise, force, pairs, reaction
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Mar28-10, 09:53 PM
P: 1
Hi guys,

What is the reason for action-reaction force pairs to arise?
Is it a consequence of electrostatic repulsion due to interaction of the 2 bodies, or can it be explained using energy conservation or momentum conservation.

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Mar29-10, 05:02 AM
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P: 7,032
Quote Quote by echolett View Post
What is the reason for action-reaction force pairs to arise?
It's an axiom or postulate that is just assumed to be self-evident and true. I'm not sure there's a way to prove it. Almost all forces invoved some type of reaction if you look at a situation from a large enough scale, and consider things like how much the earth is affected by a car acclerating on it's surface.

In some cases, a Newton 3rd law pair doesn't require physical contact, such as gravity, where the third law pair is the equal and opposing attractive force on each body in a two body system.
Mar29-10, 03:08 PM
P: 824
You could derive force pairs from momentum conservation of arbitrary pairs of objects, but we tend to think of actio = reactio as being more fundamental.

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