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Homework Help: Moment of Inertia of a Wagon Wheel

  1. Apr 6, 2007 #1
    A wagon wheel is constructed as shown in the figure. The radius of the wheel is 0.300 m, and the rim has mass 1.36kg . Each of the eight spokes, that lie along a diameter and are 0.300 m long, has mass 0.270kg .

    What is the moment of inertia?

    Wouldn't it just be the sum of the masses times the radius squared?

    I = 1.36(.300)^2 + .8(.270(.300^2))
  2. jcsd
  3. Apr 6, 2007 #2

    Doc Al

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    Staff: Mentor

    For the rim, yes; for the spokes, no. The mass of the rim is all at a single distance from the axis; not so for the mass of the spokes. Hint: Look up (or figure out) the moment of inertia of a thin rod about one end. (Treat the spokes as thin rods.)
  4. Apr 7, 2007 #3
    Oh! /smack That made that so much more simple. Thanks much.
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