Q. The radius of gyration of a solid sphere of radius $r$ about a certain axis is $r$. The distance of this axis from the centre of the sphere is
A) $r$
B) $0.5\ r$
C) $\sqrt{0.6}\ r$
D) $\sqrt{0.4}\ r$
Explanation
(d) $I = \frac{2}{5}mr^{2} = mk^{2}$
$k^{2} = \frac{2}{5}r^{2} \Rightarrow k = r\sqrt{0.4}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.