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Homework Help: Moment of inertia question

  1. Mar 20, 2007 #1
    1. The problem statement, all variables and given/known data

    When a ceiling fan rotating with an angular speed of 2.40 rad/s is turned off, a frictional torque of 0.227 Nm slows it to a stop in 6.65 s. What is the moment of inertia of the fan?

    2. Relevant equations

    3. The attempt at a solution

    In almost all of the moment of inertia equations, they involve a radius. there is no radius given in the problem. i tried to use K= 1/2 I w^2. Im really stuck and dont know what to do next.
  2. jcsd
  3. Mar 20, 2007 #2

    Doc Al

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    Staff: Mentor

    You don't have the data to compute the moment of inertia directly. Instead, deduce the moment of inertia by applying Newton's 2nd law for rotation. Hint: First compute the angular acceleration using kinematics.
  4. Mar 20, 2007 #3
    Thanks so much! i just got it right on the webassign
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