1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Conservation of angular momentum with energy

  1. Mar 5, 2010 #1
    Ice sketar rotates with open arms & her moment of inertia is I, rotational speed W. So, angular momentum is I*W. Energy is (1/2)I*W*W
    she folds her arms & her moment of inertia decreases to I/2. From conservation of angular momentum rotational speed became double say W*2.
    Energy became (1/2)*I/2*W*W*4 = I*W*W ( Energy is doubled, How?)

    Please tell me in this caculation where I am wrong?
  2. jcsd
  3. Mar 5, 2010 #2

    Doc Al

    User Avatar

    Staff: Mentor

    You're not wrong. The skater does work when she brings her arms in. She converts internal energy into rotational KE.
  4. Mar 5, 2010 #3
    Rotational kinetic energy isn't conserved
  5. Mar 6, 2010 #4
    OK, Very much Thanks for clearing my doubt.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook