Afreight car moves along a frictionless level railroad track at constant speed. the freight car is open on the top. a large load of sand is suddenly dumped into the freight car. what happens to the speed of the freight car?

Abatter hits a 0.140-kg baseball that was approaching him at 30 m/s and, as a result, the ball leaves the bat at 40 m/s in the reverse of its original direction. the ball remains in contact with the bat for 2.0 ms. what is the magnitude of the average force exerted by the bat on the ball?