Find the ratio of moments of inertia of the two disks of same mass and thickness but one of density 7.2 g/cm3 and the other of density 8.9 g/cm3.

We know that moment of inertiaI=MR22(of disk wrt principle axis)Given M1=M2V1d1=V2d2πR12t1d1=πR22t2d2 … (i) Given t1=t2 (thickness)So R12R22=d2d1 (from eq. (i))So M1R12M2R22=d2d1 as M1=M2⇒I1I2=d2d1⇒I1I2=8.97.2