Deduce the star's radius by treating it as a solid sphere?

Question

1) A star with the mass (M = 2.0 x 10^30 kg) and size (R = 3.5 x 10^8 m) of our sun rotates once every 35.0 days. After undergoing gravitational collapse, the star forms a pulsar that is observed by astronomers to emit radio pulses every 0.200 s. By treating the neutron star as a solid sphere, deduce its radius.

2) What is the speed of a point on the equator of the neutron star? Your answer will be somewhat too large because a star cannot be accurately modeled as a solid sphere.

Answer 1

This can be solved by using the law of conservation of angular momentum. I1w1=I2w2.

I1-->inertia of star 2*(MR^2)/5

w1-->angular vel., of star

I2--> inertia of neutron star

w2 --> angular vel., of neutron star

substituting the values in the equation we can get the answer of the radius since we know three values(I1, w1, w2). And hence I2 can be calculated to find the value of R2.