Q. A spherical solid ball of $1\ kg$ mass and radius $3\ cm$ is rotating about an axis passing through its centre with an angular velocity of $50\ radian/s$. The kinetic energy of rotation is
A) $4500\ J$
B) $90\ J$
C) $910\ J$
D) $\frac{9}{20}J$
Explanation
(d) $K_{R} = \frac{1}{2}I\omega^{2} = \frac{1}{2} \times \left( \frac{2}{5}MR^{2} \right) \times (50)^{2}$
$= \frac{1}{2} \times \frac{2}{5} \times 1 \times (0.03)^{2} \times (50)^{2} = \frac{9}{20}J$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.