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Homework Help: Uniform Lamina

  1. Nov 3, 2005 #1
    Where is the centre of mass of a semicircular lamina which is uniform? I know it is somewhere along the line of symestry, but where excactly?:confused:
  2. jcsd
  3. Nov 3, 2005 #2


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    Homework Helper

    It only takes a few moments to work it out.
    com = 4r/3pi:smile:
  4. Nov 3, 2005 #3
    Can you be of more help please?
  5. Nov 3, 2005 #4


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    Homework Helper

    Of course. Drag your mouse over the answer in my last post.
  6. Nov 4, 2005 #5


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    Science Advisor

    Surely, if you have a question like that, you know the basic formulas.

    The y-coordinate of the centroid of a region (center of mass assuming uniform density) is [tex]\frac{\int y dA}{\int dA}[/tex].
    [tex]\int dA[/tex] is, of course, the area of the region.

    Once, when I was teaching this, a student became fascinated by the word "lamina" (had never seen it before, apparently). As the last question on the final exam, I asked "What is 'lamina' spelled backwards?"

    Another student became furious with me because "That question doesn't make any sense!"
  7. Nov 8, 2005 #6
    Oh sorry. Haha. I didnt realise there was invisible ink on the paper.
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