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Homework Help: Angular acceleration

  1. Jan 14, 2010 #1
    1. The problem statement, all variables and given/known data

    A pulley has a radius of 2.70 m and a moment of inertia of 39.0 kg·m2. There is a hanging mass with a mass of 4.20 kg and it exerts a force tangent to the edge of the pulley. What is the angular acceleration of the pulley in rads/sec^2?

    r = 2.7m
    I=39kg·m2
    m=4.2kg

    2. Relevant equations

    a = t/I
    F = mg
    t = Fr

    3. The attempt at a solution

    I tried finding the torque on the pulley caused by the mass by multiplying the mass * gravity * the radius and then dividing by the moment of inertia to get the angular acceleration but I keep getting 2.8496 which is apparently wrong.
     
  2. jcsd
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