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Homework Help: Friction, Statics, Finding maximum angle and minimum coefficient of friction

  1. Nov 22, 2011 #1
    1. The problem statement, all variables and given/known data
    If the coefficient of static friction at B is μs = 0.3, determine the largest angle
    θ, and the minimum coefficient of static friction at A, so that the roller remains self-
    locking, regardless of the magnitude of the force P applied to the belt. Neglect the weight
    of the roller and neglect friction between belt and vertical surface.


    2. Relevant equations
    ƩM=0
    ƩFx=0
    ƩFy=0
    FAANA
    FBBNB=0.3NB


    3. The attempt at a solution
    I have attempted the solution quite a few times a couple of different ways. I keep getting stuck with variables that I can't solve for, so I have come to the conclusion that I am probably not going about it the right way. My first attempt, I took the moment about A, and then summed up the forces in the x and y directions, but wound up not being able to solve for θ or μA. I attached an attempt at a free body diagram, perhaps I don't have the friction forces going in the right direction? I would appreciate any help!
     

    Attached Files:

    • FBD.gif
      FBD.gif
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  2. jcsd
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