The mass of a star is 1.990×1031 kg

Question

The mass of a star is 1.990 kg and it performs one rotation in 27.70 days. Find its new period (in days) if the diameter suddenly shrinks to 0.730 times its present size. Assume a uniform mass distribution before and after.

Answer 1

So Hope M.,

The question is indeterminate! What it needed to additionally specify is that the star rotates as a solid body, i.e. the angular rotation speed at all depths from the surface is the same.

So you need to conserve angular momentum, and you need an expression for the angular momentum of a solid rotating object (sphere, or ball), as a function of total mass, angular speed, and radius.

You should be able to look each of these terms or equations up. Try!

-- Cheers, --Mr. d.