Q. Two uniform thin rods each of mass $M$ and length $l$ are placed along $X$ and $Y$ axis with one end of each at the origin. Moment of inertia of the system about $Z$-axis is
A) $\frac{3}{2}\ Ml^{2}$
B) $\frac{2}{3}\ Ml^{2}$
C) $2Ml^{2}$
D) None of these
Explanation
(b) According to theorem of parallel axes, moment of inertia of a rod about one if its ends
$= \frac{Ml^{2}}{12} + \frac{Ml^{2}}{4} = \frac{Ml^{2}}{3}$
$\therefore$ Moment of inertia of two rods about $Z$-axis=Moment of inertia of 2 rods placed along $X$ and $Y$-axis $= \frac{2Ml^{2}}{3}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.