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 that is traveling horizontally at 11.3 . Olaf's mass is 74.2 .
If the ball hits Olaf and bounces off his chest horizontally at 7.70 in the opposite direction, what is his speed after the collision?