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Question
A heavy ring of mass m is clamped on the periphery of al 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
Options
\[\frac{m v^2}{r}\] must be acting on the central particle
\[\frac{2m v^2}{r}\] must be acting on the central particle
\[\frac{2m v^2}{r}\] must be acting on the system
\[\frac{2m v^2}{r}\] must be acting on the ring.
Solution
\[\frac{2m v^2}{r}\] must be acting on the system
Total mass of the system = 2m
To move the centre of the system in a circle of radius r with a uniform speed v, the external force required is
\[\frac{2m v^2}{R}\]
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