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miamirulz29

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## Homework Statement

A skater spins with an angular speed of 8.3 rad/s with her arms outstretched. She lowers her arms, decreasing her moment of inertia by a factor of 8.9. Ignoring the friction on the skates, determine the percent of change in her kinetic energy. Answer in percent.

## Homework Equations

KE = (1/2)Iw^2

Li = Lf

**3. The Attempt at a Solution [/b**

wi = omega initial

wf = omega final

If Li = Lf,

Iwi = (I/8.9)wf

8.9wi = wf

So KEi = (1/2)I(wi^2)

KEf = (1/2)(I/8.9)(wf^2)

So KEf = (1/2)(I/8.9)(8.9wi^2)

So I(wi^2)/2 = I(8.9wi^2)/17.8

Does that mean there is no change in kinetic energy? Also, if there is a change in kinetic energy how do I convert that to a percent?

wi = omega initial

wf = omega final

If Li = Lf,

Iwi = (I/8.9)wf

8.9wi = wf

So KEi = (1/2)I(wi^2)

KEf = (1/2)(I/8.9)(wf^2)

So KEf = (1/2)(I/8.9)(8.9wi^2)

So I(wi^2)/2 = I(8.9wi^2)/17.8

Does that mean there is no change in kinetic energy? Also, if there is a change in kinetic energy how do I convert that to a percent?