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Homework Help: Find the net torque on the pulley

  1. Apr 7, 2010 #1
    1. The problem statement, all variables and given/known data

    The pulley in the figure has radius 13.0 cm and a moment of inertia 0.230 kg m^2; the pulley is constructed from a dense metal. The rope does not slip on the pulley rim. The system is released from rest.


    Find the net torque on the pulley, about its axle, due to the differing tensions in the rope on the two sides of the pulley.

    2. Relevant equations

    3. The attempt at a solution

    From earlier parts of the problem i have found the acceleration of the blocks a = 1.0m/s^2 and the velocity final of the larger falling block v = 3.16 m/s. i also found the tension in both of the ropes. T in rope attached to the larger mass was 35.2 N and the T in the rope on the smaller mass was 21.6 N

    Now i cannot find the net torque it is asking for

    I tried doing this

    t = torque

    tlarger block - tsmaller block = tnet

    T*d - T*d = tnet

    35.2N(5m) - 21.6N(5m) = tnet

    tnet = 68Nm

    This is wrong? How else can i go about this problem?

    thank you
  2. jcsd
  3. Apr 8, 2010 #2
    i was using the height instead of the radius

    i got it now :)
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