Given, mass of solid sphere =80kg radius of solid sphere, Rs=15m radius of circular disc, Rc=20m and time =1hour=60minutes=60×60sec ∴ Moment if inertia of solid sphere, Is=
2
5
MR2 =
2
5
×80×(15)2 =7200kg−m2 Similarly, moment of inertia of the disc, Ic=
1
2
MRc2 =
1
2
×80×(20)2 =16000kg−m2 Rate of change of moment of Inertia =