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Moment of Inertia of half disk

  1. Aug 26, 2009 #1
    Hello, just found this forum didn't know it existed. hopefully someone can help with this.

    I am trying to figure out the mass moment of inertia for a half disk spining around the center axis. A full disk is I=1/2*M*R^2. Would the inertia for spining a half disk around the center axis just be half of this? Not homework, something I am working on.

    Hopefully someone here can help
  2. jcsd
  3. Aug 26, 2009 #2

    Doc Al

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    Staff: Mentor


    Just to be clear: The formula will be the same, but since the mass is halved, the moment of inertia will be halved.
  4. Aug 26, 2009 #3
    Thanks for the quick responce. What was confusing me was that the half disk is rotating around what is the center (not COG) I thought it might get more complicated due to the rotation not being through the COG. thanks just 1/2 the formula for a full disk because it is half the mass. Here is an image for reference. Apreciated. (I am ignoring the small attachment point for simplicity)

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