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Homework Help: Moment of Inertia for Sphere

  1. Apr 23, 2010 #1
    Can someone please tell me the moment of inertia for a solid sphere rotating about an axis tangent to its surface?
  2. jcsd
  3. Apr 23, 2010 #2
    What does tangent to its surface mean? Where is the axis of rotation?
  4. Apr 23, 2010 #3
    The axis of rotation is touching the surface of the sphere at one point. That is the definition of tangent. Can it be treated as a point particle distance R from the axis?
  5. Apr 23, 2010 #4
    Parallel axis theorem?
  6. Apr 23, 2010 #5
    Sorry, never heard of that. It's not the goal of the assignment to figure out the moment of inertia around the axis tangent to the surface, but it would be a useful tool.
  7. Apr 23, 2010 #6
    Well look it up, it is not that difficult. It allows you to use the moment of inertia of a sphere (axis through center) to calculate the moment of inertia somewhere else as long as the other axis is parallel to the axis through the center. And finding the moment of inertia with axis through center is in almost every text book and on the internet. http://en.wikipedia.org/wiki/Parallel_axis_theorem
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