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Homework Help: Find the acceleration : block slides on a wedge

  1. Oct 21, 2012 #1
    sry for typo..it should be acceleration
    1. The problem statement, all variables and given/known data

    A block m slides down from a frictionless inclined surface (theta = 45) of a wedge, mass m, which is on a horizontal plane with coefficient of friction u. Prove that the wedge moves to the right with acceleration equal to g(1-3u)/(3-u) .

    im stuck on this question for a whole week..but still cant get the answer
    not sure if it is a question related to relative motion?
    plz help!!
    2. Relevant equations

    3. The attempt at a solution
    Last edited: Oct 21, 2012
  2. jcsd
  3. Oct 21, 2012 #2


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    Science Advisor

    As always, draw a force diagram.

    If what you want is the acceleration of the wedge, you need to know the net force on the wedge. If you can't figure it out, post your working, and a photo of your diagram if possible.
  4. Oct 21, 2012 #3

    cant get the relation of these three accelerations..
  5. Oct 21, 2012 #4


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    Science Advisor

    You have three equations in four unknowns - you just need one more. You just need to enforce that the block stays on the wedge and doesn't go flying off - kinematic equations may help.

    One minor point - your ay has the same sign as g, but you have defined +y to be up the page. It doesn't affect your maths here, but it can do in general.
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