Q: Moment of inertia of a quarter disc having mass m and radius R about axis passing through centre of disc and perpendicular to plane is

(A)I = mR²

(B)I = mR²/2

(C)I = mR²/4

(D)I = mR²/8

Solution: Moment of inertia (I) about z axis of a disc passing through centre of mass and perpendicular to the plane of disc is I_{z} = MR²/2

Since each quarter will have same moment of inertia (I)

4I= MR²/2

I_{z} = ¼MR²/2 = mR²/2

where ¼M = m = mass of each quarter of disc.