As shown below, bob A of a pendulum having massless string of length 'R' is released from 60^° to the vertical. It hits another bob B of half the…

As shown below, bob A of a pendulum having massless string of length 'R' is released from $\displaystyle 60^{\circ}$ to the vertical. It hits another bob B of half the mass that is at rest on a friction less table in the center. Assuming elastic collision, the magnitude of the velocity of bob A after the collision will be (take g as acceleration due to gravity.)