Please Read, do not cut and paste the answer. I am asking what happens when it I
ID: 1343593 • Letter: P
Question
Please Read, do not cut and paste the answer. I am asking what happens when it INCREASES!!! Not decreases as others have posted!!!
An ice skater stars a spin with her arms stretched out of the sides. She balances on the tip of one skate to turn without friction. She then pulls her arms in so that her moment of inertia increases by a factor of 2. In the process of her doing so, what happens to her kinetic energy?
A.It remains constant.
B.It decreases by a factor of 4.
C.It decreases by a factor of 2.
D.It increases by a factor of 4.
E.It increases by a factor of 2.
Explanation / Answer
Using conservation of angular momentum
I1 W1 = I2 W2
since I2 = 2 I1
W2 = (0.5) W1
Ratio of kinetic energy is given as
KE2 / KE1 = (0.5) I2 W22 / (0.5) I1 W21
KE2 / KE1 = (2) (0.5)2 = 0.5
so KInetic energy decreases by factor of 2