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Homework Help: Two blocks of mass connect to a pulley

  1. Aug 7, 2012 #1
    1. The problem statement, all variables and given/known data

    Blocks of mass and are connected by a massless string that passes over the pulley in the figure . The pulley turns on frictionless bearings, and mass slides on a horizontal, frictionless surface. Mass is released while the blocks are at rest.

    2. Relevant equations

    I found a1 for the mass of block one (m1).
    a1 = m2g/(m1+m2)
    T = (m1*m2*g) / (m1 + m2)
    and tension in the string (which is the same everywhere)

    3. The attempt at a solution

    Now I must find a1 with a mass of the pulley (mp) and radius R.

    So far I have drawn my free body diagrams for block 1, block 2, and the pulley. I was able to sum up my forces but I am having trouble summing up the net torque. Will the tensions from the two block be separated? Like this Tnet = r*T1 + r*T2
    Last edited: Aug 7, 2012
  2. jcsd
  3. Aug 7, 2012 #2


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    welcome to pf!

    hi kitsunebell74! welcome to pf! :smile:
    yes, the tensions will be different, and τnet = r*T1 - r*T2

    now apply the rolling constraint a = rα :wink:
  4. Aug 8, 2012 #3
    Thanks for the greeting. I figured it out. :)
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