Q.

A, B and C are disc, solid sphere and spherical shell respectively with same radii and masses. These masses are placed as shown in figure.

The moment of inertia of the given system about PQ is x15I, where I is the moment of inertia of the disc about its diameter. The value of x is _________.       [2025]


Ans.

(199)

All bodies have same mass and same radius.

Disk, IA=mR24=I

Solid sphere, IB=75mR2

Spherical shell, IC=53mR2

IPQ=mR24+(25mR2+mR2)+(23mR2+mR2)

IPQ=15mR2+24mR2+60mR2+40mR2+60mR260

IPQ=19960mR2=19915(mR24)=19915I