Question

Three thin uniform rods each of mass m and length l are placed along the three axes of a Cartesian co-ordinate system with their one end at the origin. The moment of inertia of the system about z-axis is

• A. $\frac{m{l}^2}{3}$
• B. $\frac{2m{l}^2}{3}$
• C. $\frac{m{l}^2}{6}$
• D. $m{l}^2$

Answer 1

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

MI about z axis,
$I=\frac{m{l}^2}{3}+\frac{m{l}^2}{3}+0$
$=2\frac{m{l}^2}{3}$