A heavy ring of mass m is clamped on the periphery of a light circular disc. A small particle having equal mass is clamped at the centre of the disc. The system is rotated in such a way that the centre moves in a circle of radius r with a uniform speed v. We conclude that an external force
(a) mv2/r must be acting on the central particle
(b) 2mv2/r must be acting on the central particle
(C)2mv2/r must be acting on the system
(d) 2mv2/r must be acting on the ring.

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1 Answers

(c) 2mv2/r  must be acting on the system

Explanation: 

Since the heavy ring and the small particle have equal masses, the center of mass of the system will be at r/2 from the ring. Hence the force acting on the system =mv²/(r/2) = 2mv²/r.

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