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Homework Help: Newton's Laws w/friction

  1. Feb 5, 2008 #1


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    1. The problem statement, all variables and given/known data
    A block of mass.5kg rests on the inclined surface of a wedge of mass 2kg. The wedge is acted on by a horizontal force F and slides on a frictionless surface. (a) If the coefficient of static friction between the wedge and the block is .8 and the angle of incline is 35 degrees, find the max and min values of F for which the block does not slip.

    2. Relevant equations
    Ff= mu(Fn)
    Free Body Diagrams-- sum of forces

    3. The attempt at a solution
    I drew a free body diagram and all, but then realized that I only know that when the coefficient of friction is kinetic, then it is greater than or equal to, which helps to provide a min and max, however, how can that be computable with static friction, when it is actually equal to force of friction.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Feb 6, 2008 #2
    You really are looking for the static friction coefficient, after all the block is not moving until you reach that very threshold. Just add all your vector components and it ought to be pretty straight forward, I would suggest a rotated coordinate system.
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