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Moment of inertia of a merry-go-round

  1. Feb 6, 2008 #1
    In a certain problem I was working on, it asks for the inertia of a merry-go-round, and my first instinct was that it would be the inertia of a disk about its central axis I=(1/2)MR^2, but the solution actually uses I = MR^2 the rotational inertia of a hoop about the central axis. Why do they choose the hoop and not the disk? There is nothing mentioned about how the mass is spread out, just that there is a merry-go-round.
  2. jcsd
  3. Feb 6, 2008 #2


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    The merry-go-round I picture have horses around the outer edge that the kids (or bigger kids!) sit on, so most of the mass is at the outer edge - hence a hoop.
    It is a bit unfairly worded as a question though.
  4. Feb 6, 2008 #3
    ahhh, yeah, see it said a merry-go-round at a playground so I was thinking of that thing where there are just bars extending from the center and you have to hold on as it spins really fast. I don't know what it is called but I thinked that they stopped making them for safety reasons. Those things were sweet and great examples of basic physics concepts.

    Anyway, thanks for pointing that out. It makes more sense now.
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