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Homework Help: Moment of Inertia of a disk (question on formula involving radius)

  1. Sep 17, 2008 #1
    1. The problem statement, all variables and given/known data
    Determine the moment of inertia of a think disk of mass M, with inner radius A and outer radius B, when rotating about an axis perpendicular to the plane of the disk and through its center.

    2. Relevant equations
    The equation of moment of inertia for a disk is I = (m*r^2)/2
    my question is that because there are two radii, how does that affect r in the equation?

    3. The attempt at a solution
    I = (m*r^2)/2 then substitute I = (M*r^2)/2 but is r=(B-A)^2 or is r=(B^2-A^2)?
    Last edited: Sep 17, 2008
  2. jcsd
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