Question
Two rings of same mass and radius R are placed with their planes perpendicular to each other and centres at a common point. The radius of gyration of the system about an axis passing through the centre and perpendicular to the plane of one ring is
Joshi sir comment
The axis passing through the centre of one ring and perpendicular to the plane will be diametric axis of the other ring
so moment of inertia about that axis = MR2 + 1/2 MR2 = 3/2 MR2
now compare it to Mk2 and get k, it is radius of gyration