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Homework Help: Calculating Moment of Inertia

  1. Apr 13, 2009 #1
    Damn! wrote that in the wrong forum!!
    mods please move to introductory physics!

    I'm learning by myself physics of rigid bodies , and I find it kinda hard.
    Well, I know calculating the moments of Inertia is useless cause You have a table with all the MoI.
    This is not a specific problem i ran into but I'll write it anyway:
    1. The problem statement, all variables and given/known data
    Calculate the Moment of inertia of a rotating(about it's center of mass) solid wheel of mass M( assume it's homogeneous)

    2. Relevant equations

    I= integral of something :PPP

    3. The attempt at a solution
    well i just know that the moment of inertia of a ring of mass M is MR^2/2
    seems kinda intuitive,I'd like to know how do I (using integrals) calculate the MoI of a solid sphere as stated above.
    Thank you in advance!
    Any advice\comment appreciated.
  2. jcsd
  3. Apr 13, 2009 #2
    [itex]I_{ij}(O)=\int_V dV \rho(r) \left( r^2 \delta_{ij} -r_i r_j \right)[/itex]
  4. Apr 13, 2009 #3
    Could You explain/expand about the formula? how did You pick the limits and etc.
    thanks :D appreciated
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