A bead of mass '\( m \)'slides without friction on the wall of a vertical circular hoop of radius '\( R \)' as shown in figure. The bead moves under the combined action of gravity and a massless spring \( (k) \) attached to the bottom of the hoop. The equilibrium length of the spring is '\( R \)'. If the bead is released from top of the hoop with (negligible) zero initial speed, velocity of bead, when the length of spring becomes '\( R \)', would be (spring constant is '\( k \)', \( g \) is acceleration due to gravity).
