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Question:

Three objects, A:(a solid sphere), B: (a thin circular disk) and C:(a circular ring), each have the same mass M and radius R. They all spin with the same angular speed ω about their own symmetry axes. The amounts of work (W) required to bring them to rest, would satisfy the relation.

WB>WA>WC

WA>WC>WB

WC>WB>WA

WA>WB>WC

Solution:

Work done is change in kinetic energy. Hence more the kinetic energy, more will be the work done. K.E.=Iw²/2 They all have the same angular velocity. Hence more the moment of inertia, more the kinetic energy and hence more will be the work done. Hence WC>WB>WA