PHYSICS · Multi-part · CBSE · Physics · System of Particles and Rotational Motion · System of Particles and Rotational Motion
Problem
Soon after a supernova explosion, a newly formed neutron star can be modeled as a uniform solid sphere of mass 2.0×1030kg (approximately one solar mass) and radius 10km. Observations indicate that it rotates once every 4.0h. Over time the star cools and contracts to a new radius of 8.0km without losing mass. Assume no external torques act on the star during the contraction and treat the star as a uniform sphere both before and after.
(a) Determine the new rotation period of the neutron star after it has contracted to the smaller radius.
(b) By what factor did the star’s rotational kinetic energy change as a result of the contraction? Express your answer as a numerical ratio Kfinal/Kinitial.