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Homework Help: Trouble finding the acceleration

  1. Sep 23, 2007 #1
    A block of mass m1 is attached to a massless, ideal string. This string wraps around a massless pulley and then wraps around a second pulley that is attached to a block of mass m2 that is free to slide on a frictionless table. The string is firmly anchored to a wall and the whole system is frictionless.

    I want to find the vertical acceleration a1 in terms of m1, g and T

    I know that the tension T is equal everywhere in the string and also that the acceleration af block m1 must be equal to the acceleration of block m2.

    I've tried some calculations but I always seem to get stuck with m2 in my equations.

    T = m1*g and T = (m2*a2)/2
    Last edited: Sep 23, 2007
  2. jcsd
  3. Sep 23, 2007 #2


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    The setup is that a falling weight M1 pulls a mass M2 horizontally - correct.
    The force downward on M1 is just f = M1 g and the force upward from the string is f = M2 a
  4. Sep 23, 2007 #3
    Yeah, I figured that one out but that was not the question (but thanks thanks anyway for replying! :)

    My problem is to find the a1 in terms off m1, g and T (When T = (m2*a2)/2)
  5. Sep 23, 2007 #4
    Ok. I've got the answer! Was a bit hard but finally.

    a1 = (m1-g)/m1
  6. Sep 23, 2007 #5
    are you sure ?
    i did not do the math, but the UNIT of (m1-g)/m1 is not a unit of acceleration

    Correct me if I am wrong.
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