The rotational inertia of a collapsing star changes to one third its initial value while conserving angular momentum. What is the ratio of the new rotational kinetic energy to the initial kinetic energy?

Answer 1

I guess the moment or inertia is 1/3 of original
If I w is constant then w' = 3 w
then if original Ke = (1/2) I w^2
the final is (1/2)(I/3)(9w^2)
= 3 times original

has to do work to pull mass in toward the axis of rotation against centripetal force.