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 the 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?
I'm not sure where to start this problem. Any help is appreciated!

1 answer

.280*v=.280v'+m*.140

solve for v'
Then, put that into...
1/2 .280 v^2=1/2 .280 v'^2 + 1/2 m .140^2
then solve for m.