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Find the moment of inertia of a hoop

  1. Oct 25, 2006 #1
    Find the moment of inertia of a hoop (a thin-walled, hollow ring) with mass M and radius R about an axis perpendicular to the hoop's plane at an edge.

    I know that I=n*m*r^2
    where n is the inertial constant

    but i think my main problem with this is where the axis of rotation is, im thinking that it is through the center of the ring but cant be sure any help would be great.
  2. jcsd
  3. Oct 26, 2006 #2


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    Homework Helper

    Suppose the ring is lying horizontally flat, and a vertical axis is passing through the centre of the ring. Now bodily move the axis in a horizontal direction, so that the axis is now passing through the edge, or circumference, of the ring. This new position for the axis shows you the intended axis of rotation for your problem.
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