A star of mass twice the solar mass and radius 10^6 km rotates about its axis with an angular speed of 10^-6 rad/s^-1.
A star of mass equal to two solar masses and radius 106 km rotates about its axis with an angular speed of 10-6 rads-1. What is the angular speed of the star, when it collapses (due to inward gravitational forces) to a radius of 104 km?
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Here, R1 = 106 Km
ω1 = 10-6 rads-1, ω2 = ? R2 = 104 Km
As I1ω1 = I2ω2
\(\therefore\) ω = \(\frac{I_1\omega_1}{I_2}=\cfrac{\frac25MR_1^2\omega_1}{\frac25MR_2^2}\)
\(=(\frac{R_1}{R_2})^2\)ω1
ω2 = \(\left(\frac{10^6}{10^4}\right)\)x 10-6 = 10-2 rad/s
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