NDA 2019 Physics question

A thin disc and a thin ring, both have mass M and radius R. Both rotate about axes through their center of mass and are perpendicular to their surfaces at the same angular velocity. Which of the following is true ?

(A)The ring has higher kinetic energyCorrect
(B)The disc has higher kinetic energy
(C)The ring and the disc have the same kinetic energy
(D)Kinetic energies of both the bodies are zero since they are not in linear motion

Answer: (A)

Solution

Rotational kinetic energy is . For the ring and for the disc . At the same the ring,

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Question ID VK-031442