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Homework Help: Find mass of pulley

  1. Apr 10, 2009 #1
    1. The problem statement, all variables and given/known data
    A light string is wrapped around the outer rim of a solid uniform cylinder of diameter 75.0cm that can rotate without friction about an axle through its center. A 3.00kg stone is tied to the free end of the string. When the system is released from rest, you determine that the stone reaches a speed of 3.50m/s after having fallen 2.50m.

    What is the mass of the cylinder?

    2. Relevant equations
    net torque = I * alpha
    I = m * r^2 / 2

    3. The attempt at a solution
    For this problem I have no idea where to start. I am completely lost...I know there should be some Omega calculations a theta calculations and I need to find impulse along with torque...any help is appreciated!
  2. jcsd
  3. Apr 10, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    You need to analyze both the pulley and the falling stone. Write Newton's 2nd law for each, then combine the equations to relate pulley mass to the acceleration of the stone.

    Use the given data to determine the acceleration of the stone.
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