Four particles, each of mass m, are kept at the four corners of a square of edge a. Moment of inertia of the system about the line perpendicular to the plane of the square and passing through the centre of the square is
The perpendicular distance of every particle from the given line is a√2
The moment of inertia of one particle is m(a√2)2 = ma22
The moment of intertia of system is therefore = 2ma2