Conservation of angular momentum with energy

  • #1

Main Question or Discussion Point

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?
 

Answers and Replies

  • #2
Doc Al
Mentor
44,882
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You're not wrong. The skater does work when she brings her arms in. She converts internal energy into rotational KE.
 
  • #3
1
0
Rotational kinetic energy isn't conserved
 
  • #4
OK, Very much Thanks for clearing my doubt.
 

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