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Homework Help: A pulley with two masses

  1. Apr 2, 2008 #1
    Let me start off by saying I'm new here and I hope I did this in the format. Thank you.

    1. The problem statement, all variables and given/known data

    Two masses, M1= 35.0 kg and M2= 38.0 kg, are connected by a rope that hangs over a pulley. The pulley is a uniform cylinder of radius 0.381 m and mass 3.5 kg. Initially M1 is on the ground and rests 2.5 m above the ground. If the system is released, use conservation of energy to determine the speed of just before it strikes the ground. Assume the pulley bearing is frictionless.

    2. Relevant equations

    F= m*a Torque= r x F

    3. The attempt at a solution

    I found the tension that M2-M1 put on the pulley.

    F=(38.0-35.0)*9.8= 29.4

    I'm a little lost after that. How do I find the speed of the pulley?
  2. jcsd
  3. Apr 2, 2008 #2
    The problem tells you to use conservation of energy. Have you done that? What types of energy are present in the beginning and when the mass hits the ground?
  4. Apr 2, 2008 #3
    i have the same problem is the equation for acceleration

    a = (m2-m1)g/{(m1+m2)+.5m}
  5. Apr 2, 2008 #4

    I got it now.
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