A smooth solid cylinder is rolling on a smooth horizontal surface without slipping. If collides elastically with an identical cylinder at rest. After the collision, ratio of the kinetic energy of the first cylinder to that of the second cylinder is

Since the collision is elastic, the cylinders will interchange their linear velocities. Also since the cylinders are smooth, rotational motion of te first cylinder will not be transferred to the second cylinder. ∴ K1K2=12Iω212mV2=12(12mR2)ω212m(ωR)2=12