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Homework Help: Torque applied pully with mass

  1. Mar 27, 2009 #1
    An Atwood's machine consists of blocks of masses m1 = 8.4 kg and m2 = 20.7 kg attached by a cord running over a pulley as in the figure below. The pulley is a solid cylinder with mass M = 7.40 kg and radius r = 0.200 m. The block of mass m2 is allowed to drop, and the cord turns the pulley without slipping.

    (a) Why must the tension T2 be greater than the tension T1?

    (b) What is the acceleration of the system, assuming the pulley axis is frictionless?

    (c) Find the tensions T1 and T2.

    Does anyone have idea how pully w/ mass works?
  2. jcsd
  3. Mar 27, 2009 #2
    Treat the pulley as a third body and draw three FBDs. Since the cord does not slip on the pulley, you have the tensions acting on the two sides of the pulley acting to give it an angular acceleration.
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