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Homework Help: I need help with rotational kinetic energy problems

  1. Mar 10, 2015 #1

    I tried to use this formula: KE=(1/2)(I)(w)^2, and work=change in KE

    For the first question, i tried to plug the number into the rotation kinetic energy formula:
    I found out this was the answer 1.1 x 106 J, but I got 2218410J

    For the second one, I did:
    And I got 21j, pretty sure is wrong.

    Can someone please help me out, or give me a hint??
    Really struggling.
    Does the change in kinetic energy equal to work?
    Last edited by a moderator: Mar 10, 2015
  2. jcsd
  3. Mar 10, 2015 #2


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    Science Advisor
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    I get about the same.
    What's the formula for the MoI of a solid uniform sphere?
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