Question

Three rods each of length L and mass M are placed along X, Y and Z-axes in such a way that one end of each of the rod is at the origin. The moment of inertia of this system about Z axis is

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

Moment of inertia of the system about z-axis can be find out by calculating the moment of inertia of individual rod about z-axis
$I_1=I_2=\frac{M{L}^2}{3}$ because z-axis is the edge of rod 1 and 2
and $I_3=0$ because rod in lying on z-axis
$\therefore I_{System}=I_1+I_2+I_3=\frac{M{L}^2}{3}+\frac{M{L}^2}{0}+0=\frac{2M{L}^2}{3}.$