Question

Three uniform and thin rods each of mass $M$ and length $l$ are placed along the three coordinate axes with one end at the origin.The moment of inertia of the system about the X axis is:

• A. $2M{l}^2$
• B. $\frac{2}{3}M{l}^2$
• C. $\frac{3}{2}M{l}^2$
• D. $\frac{1}{2}M{l}^2$

Answer 1

The correct option is B $\frac{2}{3}M{l}^2$

Moment of inertia of rod1 along x axis will be zero.

$\therefore I_X=\frac{M{L}^2}{3}+\frac{M{L}^2}{3}+0$

$=\frac{2M{L}^2}{3}$