Under some circumstances, a star can collapse into an extremely dense object made mostly of neutrons and called a neutron star. the density of a neutron star is roughly 1014 times as great as that of ordinary solid matter. suppose we represent the star as a uniform, solid, rigid sphere, both before and after the collapse. the star's initial radius was 7.0×105km (comparable to our sun); its final radius is 15 km.

The question is incomplete however this kind of questions about determinate the angular speed and taking a reference of days rotating the first star.

w=0.11312 rad/s

Explanation:

The situation is about a two star the question is incomplete, miss the time rotate one star so we assume the first star rotated once in 30 days so:

Angular momentum

The inertia

The momentum must be conserved so

notice don't have to know the mass or use the density however at the end can determinate

Time can determinate the frequency so determinate angular speed of the first star

the answer is neither ball has a charge.

because if they were both positively charged, they will repel each other.

if they were positively and negatively charged, they will seek.

grav potential energy