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Homework Help: Rotational Dynamics and pulley

  1. May 1, 2009 #1


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    1. The problem statement, all variables and given/known data

    Two weights are connected by a very light flexible cord that passes over a 50 N frictionless pulley of radius .300 m. Pulley is a solid uniform disk and is supported by a hook connected to a ceiling. What force does the ceiling exert on the hook? There are two weights around each side of the disk, one is 75 N and the other is 125 N. Answer is 249 N.

    2. Relevant equations

    I = 1/2 MR^2

    3. The attempt at a solution

    Attached Files:

    • mg2.bmp
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  2. jcsd
  3. May 1, 2009 #2


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    Homework Helper

    Hi J89! :smile:

    (I assume that "frictionless pulley" means that there is friction between the pulley and the rope, with no slipping)

    The tension in the two sections of rope will be different … call them Tm and TM, and call the linear acceleration a …

    then apply good ol' Newton's second law three times, ie to each of the weights and the pulley (separately), to get Tm + TM :wink:
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