A heavy ring fo 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 of mass moves in a circle of radius r with a uniform speed v. We conclude that an external forec :
A. `(mv^2)/r` must be acting on the central particle
B. `(2mv^2)/r` must be acting on the central particle
C. `(2mv^2)/r` must be acting on the system
D. `(2mv^2)/r` must be acting on the ring
