A 70 kg person is riding on a frictionless skateboard at 5 m/s. A friend facing him throws a 5 kg ball toward him at 20 m/s. What is his final speed after catching the ball?
conserve momentum:
70*(+5) + 5(-20) = (70+5)v
v = +10/3
70*(+5) + 5(-20) = (70+5)v
v = +10/3