Question

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.

Answer 1

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

Step-by-step 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

`P_(m)=I*w`

The inertia

`I=(3)/(5)*m*r^2`

The momentum must be conserved so

`P_(m1)=P_(m2)`

`I_(1)*w_(1)=I_(2)*w_(2)`

`(2)/(5)*m*r_(1)^2*w_(1)=(2)/(5)*m*r_(2)^2*w_(2)`

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

`w_(2)=(r_(1)*w_(1))/(r_(2))`

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

`w_(1)=2\pi*f_(1)`

`t_(1)=30days*(24hr)/(1day)*(60minute)/(1hr)*(60s)/(1minute)=2592000s`

`f_(1)=(1)/(t_(1))=(1)/(2592000)=3.858x10^-7Hz`

`w_(1)=2.424x10^(-6)(rad)/(s)`

`w_(2)=(7.0x10^8m)/(15x10^3m)*2592000`

`w_(2)=0.11312 rad/s`