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Homework Help: Moment of inertia, double integral

  1. Apr 14, 2014 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
    For part B, why is he using the formula for the moment of inertia about the y-axis? Why isn't he using the formula for the moment of inertia about the origin?


    The formula that I'm referring to is the "polar moment of inertia" in this list.
  2. jcsd
  3. Apr 14, 2014 #2


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    Gold Member

    We can't read any problem statement and relevant equations in you post.
    What's the question?

    Note that a moment of inertia is always defined with respect to an axis (of rotation).
    There is nothing like a moment of inertia about a point like the origin.
  4. Apr 14, 2014 #3
    You can't see the picture? I can see it :/.

    The formulas are in the link.
    I don't know what to tell you. The problem is asking for moment of inertia about the origin. The list of integrals also has a formula for "polar moment of inertia".
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