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Homework Help: Friction, inclined plane.

  1. Apr 21, 2007 #1
    1. The problem statement, all variables and given/known data
    This is a conceptual/logic question I have. I don't understand why for minimum P: P must be perpendicular to R; angle beta = psi_s. (please see attached picture). Once I can get my arms around that statement, I can solve the problem. Thanks for any logic help. Or if there's another way to approach this, that's cool too.

    2. Relevant equations

    3. The attempt at a solution
    Why is the angle Beta not = 0? That is the most puzzling thing conceptually. It would seem that if angle Beta=0, you would get the most mechanical efficiency because the direction of force P would then be perpendicular to the normal N.

    Attached Files:

    Last edited: Apr 21, 2007
  2. jcsd
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