Physics Help Forum Newton's Third Law textbook problem

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 Sep 6th 2016, 02:23 AM #1 Junior Member   Join Date: Sep 2016 Posts: 1 Newton's Third Law textbook problem Imagine that I am pushing on a wall. Then my textbook says that by Newton's third law, F A B = F B A FAB=FBA, where I am B and the wall is A. Isn't this wrong? Shouldn't it be that F A B = − F B A FAB=−FBA? __________________
 Sep 6th 2016, 01:58 PM #2 Physics Team     Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,324 I believe they are talking about the magnitudes of the forces F_AB and F_BA. Per newton's 3rd law the forces are equal in magnitude and opposite in direction. So you are correct if F_AB and F_BA are vectors, not scalars.

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