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Homework Help: Homework help regarding forces of friction and their directions

  1. Apr 29, 2007 #1
    The Problem

    http://img15.imgspot.com/u/07/118/16/friction.JPG [Broken]

    What I Think

    http://img15.imgspot.com/u/07/118/16/think.JPG [Broken]

    The Correct Solution

    http://img15.imgspot.com/u/07/118/16/solution.JPG [Broken]

    What Is Confusing Me

    Shouldn't the force of friction on the slab be pointed to the left? I knew the force of friction on the block is pointed to the left (because friction will oppose movement), so I naturally assumed this force to the left also acts on the slab (the two surfaces are touching after all).

    I just cannot see why the friction force on the slab is to the right.

    Thanks a lot! :)
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Apr 29, 2007 #2
    Picture instead of the slab remaining stationary and the block sliding right, the block standing still and i the slab is sliding left. . . then which direction will oppose motion direction?
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