[填空题]
A 0.280-kg croquet ball makes a4y (ksg o-k+0zlcd o,pn5 : 0;opox5tmykopo:hkai, ) e elastic head-on collision with a second ball initially at rest. The second ball moves off with half the original speedak):ipye: ok;5xooh,o p t05 m of the first ball.
(a) What is the mass of the second ball? kg
(b) What fraction of the original kinetic energy $(\Delta\mathrm{kE/KE})$ gets transferred to the second ball?
