Q. A solid sphere of mass $M$ and radius $R$ spins about an axis passing through its centre making 600 rpm. Its KE of rotation is
A) $2/5\pi^{2}MR$
B) $\frac{2}{5}\pi^{\ }M^{2}R^{2}$
C) $80\pi^{2}MR^{2}$
D) $80\pi^{\ }R$
Explanation
(c) KE of rotation $= \frac{1}{2}I\omega^{2} = \frac{1}{2} \times \frac{2}{5}MR^{2}(2\pi{n)}^{2}$
$= \frac{1}{5} \times 4\pi^{2}n^{2}MR^{2}$
$= 0.8\pi^{2}\left( \frac{600}{60} \right)^{2}MR^{2} = 80\pi^{2}MR^{2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.