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2011 F=ma #13

  1. Jan 31, 2012 #1
    1. The problem statement, all variables and given/known data
    The apparatus in the diagram consists of a solid cylinder of radius 1 cm attached at the center to two disks of radius 2 cm. It is placed on a surface where it can roll, but will not slip. A thread is wound around the central cylinder. When the thread is pulled at the angle θ = 90◦ to the horizontal (directly up), the apparatus rolls to the right. Which below is the largest value of θ for which it will not roll to the right when pulling on the thread?

    The figure can be found at www.aapt.org/physicsteam/2012/upload/WebAssign-exam1-2011-1-4.pdf (Problem 13)

    2. Relevant equations
    τ=Fr sinθ
    I'm not sure about others; maybe the ones relating angular/translational kinematics


    3. The attempt at a solution

    I'm confused. Isn't the only torque caused by the force on the thread, so wouldn't the discs always roll to the right?...
     
  2. jcsd
  3. Feb 1, 2012 #2

    tiny-tim

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    hi usamo42! :smile:
    what about the torque of the friction force? :wink:
     
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