Question
Calculate the radius of gyration of hollow sphere about its diameter and tangent.

Solution
Let M be the mass and R be the radius of hollow sphere.
(i) Radius of gyration about diameter:
Moment of inertia of hollow sphere about diameter is,
If Kd is radius of gyration about diameter then,
(ii) Radius of gyration about tangent:
Moment of inertia of hollow sphere about tangent can be calculated by using the theorem of parallel axis.
That is,
If Kt is radius of gyration about tangent then,