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Acceleration of two masses on a pulley

  1. Jun 26, 2010 #1
    1. The problem statement, all variables and given/known data
    Find the acceleration of the block on the left in terms of M, m and g.
    See attachment

    2. Relevant equations
    F=ma


    3. The attempt at a solution
    From the free body diagram,
    -Mg+Mg+mg=(m+M)*a
    a=m*g/(m+M)

    I think this is correct, however the solution states the correct answer as
    a=m*g/(m+2M), indicating a problem with the signs.
     

    Attached Files:

  2. jcsd
  3. Jun 26, 2010 #2

    rl.bhat

    User Avatar
    Homework Helper

    While finding the acceleration of the masses, you have to take into account the tension in the string.

    (M +m)g - T = (M+m)a......(1)

    T - mg = ma. ..........(2)

    Now solve for a.
     
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