Conservation on Angular Momentum

[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?

 

[hage567]

What have you tried so far? Please show us your work.

 

[misskk24]

:\

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

 

[hage567]

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

 

[misskk24]

L=mvr

?

 

[misskk24]

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

 

[hage567]

L=mvr

?

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

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

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?