Physics

Problem

A star can be approximated as a uniform solid sphere. It rotates once every 25 days when its radius is

7.0\times10^{8}\,\text{m}

. Later in its life it collapses gravitationally to a radius of

1.0\times10^{4}\,\text{m}

while its mass remains nearly the same and external torques are negligible. What is the rotation period of the star after the collapse? a)

4.4\times10^{-5}\,\text{s}

4.4\times10^{-3}\,\text{s}

4.4\times10^{-4}\,\text{s}

4.4\times10^{-2}\,\text{s}