1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 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


    User Avatar
    Science Advisor
    Homework Helper

    hi usamo42! :smile:
    what about the torque of the friction force? :wink:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook