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Homework Help: Velocity problem

  1. Apr 24, 2005 #1
    A hoop with a radius of .5m and mass of .2kg is released from rest and rolls down inclined plane. How fast is it moving after dropping from vertical distance of 3m? First I tried v=Iw/md but I had no info for angular velocity so I tried calculating using v=sq root 2xgxh and get 7.7m/s but my online test is saying it is wrong. Am I using the wrong formula?
  2. jcsd
  3. Apr 24, 2005 #2


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    Energy will be conserved. You seem to have some idea what moment of inertia and angular velocity are, so you are not far away from the result. Kinetic energy can be broken into the kinetic energy of transaltion and the kinetic energy of rotation. The first depends on linear velocity of the center of mass. The second depends on angular velocity about the center of mass. Firgue out the connection between those velocities assuming the hoop is NOT SLIPPING.
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