Question

The moment of inertia of a solid sphere (Mass= M,Radius=a) about a diameter is

Answer 1

Moment of inertia of a solid sphere is:

$$I = \dfrac25Ma^2$$

where $M$ is its mass, and $a$ is its radius.

See detailed derivation here (http://hyperphysics.phy-astr.gsu.edu/hbase/isph.html).

Answer. $I = \dfrac25Ma^2$.