Conservation of Angular Momentum of Star

[ganondorf29]

Homework Statement

The mass of a star is 1.51·1031 kg and its angular velocity is 1.50E-7 rad/s. Find its new angular velocity if the diameter suddenly shrinks to 0.49 times its present size. Assume a uniform mass distribution before and after. Icm for a solid sphere of uniform density is 2/5 mr2

Homework Equations

L=Iw

L(int)=L(final)

The Attempt at a Solution

L(int) = [(2/5)M*R^2]*(wint)
L(final) = [(2/5)M*(0.49)*R^2]*(wfinal)

And I got stuck there. I don't know how to find the radius and I think that's holding me back.

 

[hage567]

Note that it will cancel out when you set them equal since you've expressed the final radius in terms of the initial radius.

Be careful with the 0.49, it should be squared as well.