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Homework Help: Static friction on an inclined plane.

  1. Oct 17, 2009 #1
    1. The problem statement, all variables and given/known data

    http://img124.imageshack.us/img124/9997/problem3.jpg [Broken]

    2. Relevant equations

    f=mgcos theta

    3. The attempt at a solution
    I am thinking the answer is f = mgcos theta because gravity only acts on y-component but the answer is f=mgsin theta . Can anyone explain?
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Oct 17, 2009 #2


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    Homework Helper

    In the problem, f is the frictional force ,not the normal reaction.
    Frictional force acts in the opposite direction of the motion of the block.The block moves down due to the component of weight along the inclined plane. What is that component?
  4. Oct 17, 2009 #3
    x-component of weight?
  5. Oct 17, 2009 #4
    Last edited by a moderator: May 4, 2017
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