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Inertia Problem please help

  1. Jun 29, 2003 #1
    Two identical disks, with rotational inertia I (= 1/2 MR2), roll without slipping across a horizontal floor and then up inclines. Disk A rolls up its incline without slipping. On the other hand, disk B rolls up a frictionless incline. Otherwise the inclines are identical. Disk A reaches a height 12 cm above the floor before rolling down again. Disk B reaches a height above the floor of?
    I've tried a couple of things but i don't think i'm going in the correct direction...can anyone help me?
  2. jcsd
  3. Jun 29, 2003 #2
    You can readily see

    that the disc on the frictionless incline can't convert it's rotational energy into potential energy, whereas the disc on the frictional incline can covert both its translational and rotational energy into potential energy. Solving the problem is just a matter of finding the ratios of translational and rotational energies and plugging them into the formulas for total and translational only.
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