A 0.280-kg croquet ball makes an elastic head-on collision with a second ball initially at rest. The

Question:

A 0.280-kg croquet ball makes an elastic head-on collision with a second ball initially at rest. The second ball moves off with half and original speed of the first ball.
(a) What is the mass of the second ball?
(b) What fraction of the original kinetic energy (ΔKE/KE) gets transferred to the second ball?