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Rotational inertia help

  1. Oct 8, 2007 #1
    In the figure below, a constant horizontal force Fapp of magnitude 17 N is applied to a wheel of mass 6 kg and radius 0.70 m. The wheel rolls smoothly on the horizontal surface, and the acceleration of its center of mass has magnitude 1.00 m/s2.

    (a) In unit-vector notation, what is the frictional force on the wheel?

    F=ma , t=I(a/r)

    3. The attempt at a solution
    - I set up both equations with my applied force and frictional force, so I have 2 unknows in my I and frictional force. My problem is coming in not knowing what to sub in for I. I don't know whether a wheel would be considered a solid disc or a hoop. My initial thinking would be I=mr^2, and then I could plug that in into the torque equation and cancel out my r and then solve for frictional force. Would that be correct?
  2. jcsd
  3. Oct 9, 2007 #2


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    A wheel would be a hoop... hence I = mr^2.
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