As shown below, bob \( A \) of a pendulum having massless string of length \( 'R' \) is released from \( 60^\circ \) to the vertical. It hits another bob \( B \) of half the mass that is at rest on a frictionless 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.)
