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Question:
I am having difficulty explaining Newton's Third Law of Motion in regard to every action force has an equal and opposite reaction force. in that case how does anything move?



Replies:
F net = ma
and F1,2 = -F2,1

So let us say mass one is a person and mass two is Earth. To walk, you push against Earth just as hard as Earth pushes on you.

so:
M earth (a) = -m person (A)

Wince these are equal and opposite products, the smaller mass will have the main acceleration.

---Nathan A. Unterman

A good conceptual physics source that is easy to read and will help you is: Paul Hewitt "Conceptual Physics" Addison-Wesley



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