Centre of Mass Frame - Examples | ABJ Sir

Two identical small balls A and B each of mass m connected by a light inextensible string of length l are placed on a frictionless horizontal floor. With what velocity u must the ball B be projected vertically upwards so that the ball A leaves the floor A small ring /bead of mass m can slide on a smooth straight wire and a particle of mass 2m attached to the ring by a light inextensible string of length L. The particle is held in contact with the wire and with the string taut and is then let fall. Find the tension in the string when the string makes an angle with the wire.