moment of inertia of spherical shell?

Answer 1

The moment of inertia of a sphere is:

(2/5)* M * R^2

For a hollow sphere (spherical shell) you can subtract the hollow part from the sphere part, but since the M (mass) term will change based on diameter it is easier to substitute:

M = p * 4/3 * PI * R^3 (p = density)

So.. in the end you get I = 0.5333 p ( R2^5 - R1^5 )

Where R2 = Outer Radius, R1 = Inner Radius

Answer 2

Adding to what Leonardo said, if it's just a thin shell so the thickness can be ignored,
I = (2/3)*M*R^2