The momentum of the first ball is
(0.0600 kg) (60.0 m/s) = 3.60 kg•m/s
The second ball moves at a speed v so that it has the same momentum, which means
(0.0100 kg) v = 3.60 kg•m/s
v = (3.60 kg•m/s) / (0.0100 kg)
v = 360. m/s
