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Q & A: friction and Newton's laws

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Most recent answer: 07/10/2012
Q:
Friction can be broken into two types of forces, Sliding and Static. Can these be characterized into Newton’s laws? For example does static friction fit into Newton's 3rd law and Sliding into his 1st??
- Tracey (age 17)
Tin Can Bay,Qld, Australia
A:
Newton's laws are not mere rules of thumb, they're general laws of nature. Although they have to be written carefully to work in cases where special relativity matters, for all the sorts of problems you are thinking of they should be taken as exact.

So the first, second,  and third laws all work exactly for both static and sliding friction.

Let's look at the third law, probably the most interesting here. Regardless of whether two objects (A and B) in contact are sliding or not, the friction force from A on B is exactly opposite to the friction force from B on A.

Mike W.

(published on 07/10/2012)

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