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Homework Help: Moment of Inertia Problem: Perpendicular Axes THM

  1. Feb 28, 2008 #1
    [SOLVED] Moment of Inertia Problem: Perpendicular Axes THM

    1. The problem statement, all variables and given/known data
    First, the problem asked us to basically prove the Perp. Axes Thm and then use it to prove that the MoI of a thin, uniform square sheet with mass M and side L through ANY axis in its plane is equal to 1/2 M L^2

    2. Relevant equations
    The moment of inertia for a square sheet of a perpendicular axis through its center of mass is 1/6 M L^2

    3. The attempt at a solution

    First, I tried to simply say that I_x is perp. to I_y and that their sum is I_o which is equal to 1/6 M L^2 (above). And since the square is uniform, I_x = I_y = 1/2 I_o but this gave me I_x = 1/12 M L^2. Is it possible that the book has a misprint? How is it possible for the moments of inertia of an axis in the plane to be 3 times the MoI through the center of mass?
  2. jcsd
  3. Feb 28, 2008 #2
    Nevermind, physics teacher confirms the the typo. The correct answer is what I got, I_x = 1/12 M L^2
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