# Conservation on Angular Momentum

1. Apr 15, 2008

### misskk24

A figure skater during her finale can increase her rotation rate from an initial rate of 1.02 revolutions every 2.08 s to a final rate of 3.05 revolutions per second. If her initial moment of inertia was 4.50 kg*m2, what is her final moment of inertia?

2. Apr 15, 2008

### hage567

3. Apr 15, 2008

### misskk24

:\

i'm bascially stuck
i have no idea where to begin

4. Apr 15, 2008

### hage567

Can you state what the equation for angular momentum is? What does your textbook say?

5. Apr 15, 2008

### misskk24

L=mvr

?

6. Apr 15, 2008

### misskk24

but the inertia is I=(1/2)MR^2

7. Apr 15, 2008

### hage567

You want this form

$$L = I\omega$$

Is that one in your book? L is angular momentum, I is the moment of inertia, and $$\omega$$ is the angular speed.

Maybe look around here to learn about it: http://hyperphysics.phy-astr.gsu.edu/hbase/conser.html#conamo

You don't need this, since you were given the initial value of I directly in the question. You are trying to find the final value.

So if angular momentum is conserved, what will your equation look like?