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Homework Help: Find the moment of inertia of this disk help

  1. Apr 12, 2008 #1
    1. The problem statement, all variables and given/known data

    A curcial part of a piece of machinery starts as a flat uniform cylindrical disk of radius R0 and mass M. It then has a circular hole of radius R1 drilled into it. The hole's center is a distance h from the center of the disk. Find the moment of inertia of this disk (with off-center hole) when rotated about its center, C.

    Hint: Consider a solid disk and subtract the hole; use parallel-axis theorem.

    2. Relevant equations
    L=IA


    3. The attempt at a solution

    I spent hours on paper with no end, google "chicken scratch" for proof.
     
  2. jcsd
  3. Apr 12, 2008 #2

    tiny-tim

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    … one step at a time …

    Hi Quartz! :smile:

    When you're confused, just go one step at a time …

    First step … what is the parallel-axis theorem? :smile:
     
  4. Apr 12, 2008 #3
    Thanks!

    wow great help!! this forum is the bestest!!!!!!!!!!
    so you mean I pretend it's a solid and then subtract the drilled hole?
    then with the theorem and some substitution i can get the answer!?
    wow great, thanks so much.
    too bad i handed this homework in days ago.
    but thank god you could explain it so nicely.
    Borat: NOT.
    my teacher showed it to me, but whatever.

    you people, what's the point of this forum?
     
  5. Apr 12, 2008 #4

    tiny-tim

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    The point of this forum is not to do your homework for you.

    This is a cooperative forum … we help you to do the work yourself. :smile:

    As rohanprabhu previously pointed out to you:
    And if you handed in the work days ago, why did you ask us only 14 hours ago?
     
  6. Apr 12, 2008 #5
    wans't my original post "04.10.08, 09:32"?
    and I got help from my teacher so there.
     
  7. Apr 13, 2008 #6

    tiny-tim

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    erm … no … your original post, #1 above, was "yesterday" (that's 04.12
    08) at 08.45, London time (same day, 03.45 New York time).
     
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