Two balls having masses m and 2m are fastened to two light strings of same length l which is held horizontally[say x axis, with the mass 2m at (l,0) and mass m at (-l,0)]. The strings are kept fixed at origin. This system is released from rest. Collision between the balls is elastic in nature.
a. Find the velocities of the balls just after their collision and
b. How high will the balls rise after collision?