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Homework Help: Moment of Intertia

  1. Nov 30, 2006 #1
    http://img100.imageshack.us/img100/1756/untitled2qx1.jpg [Broken]

    I am having trouble with #21. I already did #20, but I have NO idea of how to do #21. First of all, I am not really sure where is the axis suppose to be.
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Nov 30, 2006 #2


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    Use the parallel axis theorem. Put the axis through the tip of the arrow in the diagram
  4. Nov 30, 2006 #3
    Acorrding to the parallel axis theorm, you get the inertia by dong this

    I = Icm + D^2M

    Where Icm is the inertia with respect to the center, and D is the distnance, and M is the mass.

    Well, Icm is the answer I got for #20 right?

    Also, what do I use for the D? Is D the radius?

    Also, what is M? Is M the mass for the hoop plus the mass of all the 4 spokes?
  5. Nov 30, 2006 #4


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    Yes. Icm is what you found in #20.

    M is the total mass and D is the distance from the center of mass to the point of rotation. In this case, D = radius
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