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Homework Help: Complex Pulley/Force/Circular motion question.

  1. Sep 28, 2015 #1
    1. The problem statement, all variables and given/known data
    A rope is wrapped through an angle θ about a horizontal pole (So for ex-
    ample, θ = 2π would imply the rope goes around one full time). The rope and
    the pole have a static friction coeffecient of μ, and the pole is of radius r. From
    one end of the rope hangs a mass m. How much force must be exerted on the
    other end of the rope to keep the mass from falling?

    2. Relevant equations

    3. The attempt at a solution
    So I attempted to draw out FBDs for each section and I got that the string on the left side has a Fpull in the downward direciton, a tension force pulling upward and a friction force upward. On the mass, I have mg pulling down, tension and Fpull in the upward direction.

    I have the diagram uploaded.

    Attached Files:

  2. jcsd
  3. Sep 28, 2015 #2


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    Gold Member

    This situation has quite a special solution, the formula you need is named after a German scientist: Eytelwein. I don't know if your task is to derive the formula by yourself, but this wouldn't be very easy. If you want to try it you have to draw the FBD for a small piece of rope (for a small angle dθ).
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