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

Answer:

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

$P_{m}=I*w$

The inertia

$I=\frac{3}{5}*m*r^2$

The momentum must be conserved so

$P_{m1}=P_{m2}$

$I_{1}*w_{1}=I_{2}*w_{2}$

$\frac{2}{5}*m*r_{1}^2*w_{1}=\frac{2}{5}*m*r_{2}^2*w_{2}$

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

$w_{2}=\frac{r_{1}*w_{1}}{r_{2}}$

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

$w_{1}=2\pi*f_{1}$

$t_{1}=30days*\frac{24hr}{1day}*\frac{60minute}{1hr}*\frac{60s}{1minute}=2592000s$

$f_{1}=\frac{1}{t_{1}}=\frac{1}{2592000}=3.858x10^-7Hz$

$w_{1}=2.424x10^{-6}\frac{rad}{s}$

$w_{2}=\frac{7.0x10^8m}{15x10^3m}*2592000$

$w_{2}=0.11312 rad/s$