Olaf is standing on a sheet of ice that covers the football stadium parking lot in Buffalo, New York; there is negligible friction between his feet and the ice. A friend throws Olaf a ball of mass 0.400 kg that is traveling horizontally at 11.3 m/s. Olaf's mass is 75.0 kg.
(a) If Olaf catches the ball, with what speed v_f do Olaf and the ball move afterward?
(b) If the ball hits Olaf and bounces off his chest horizontally at 8.90 m/s in the opposite direction, what is his speed v_f after the collision?