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Homework Help: A question about Centre of Gravity

  1. Mar 22, 2007 #1
    1. The problem statement, all variables and given/known data
    A uniform disc A of radius 2m is cut as shown in the figure. The cut out is also a disc of radius 1m. O is the centre of gravity of disc A before cutting and O' is its centre of gravity after cutting. Find the distance between O and O'

    2. Relevant equations

    3. The attempt at a solution
    I know how to find the CG of disc A and the CG of the new disc respectively..
    But i don't know how to find out the CG of the newly cut disc A...
    I don't know what approach should I use in this question

    Can anyone help me please?

    Attached Files:

    • cg.jpg
      File size:
      51 KB
  2. jcsd
  3. Mar 22, 2007 #2
    can someone help me please?
  4. Mar 22, 2007 #3


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    Without viewing your attachment nobody can help you.
  5. Mar 22, 2007 #4
    First question: How do you find the center of gravity of an object?
  6. Mar 22, 2007 #5

    Doc Al

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    Staff: Mentor

    I assume you can find the center of mass of two overlapping solid discs. Hint: What kind of disc would you have to add to disc A to get a hole of the right size and placement? Hint2: A + -B = A - B (It's a mathematical trick!)
  7. Mar 23, 2007 #6
    I know how to do it now~ Thanks a lot
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