An open railroad car of mass 20,000 kg is rolling without friction at 5 m/s along a level track when it starts to rain. After the car has collected 2000 kg of water, the rain stops.

(a) What is the car's velocity?

(b) As the car is rolling along, the water begins leaking out of a hole in the bottom at a rate of 5 kg/s. What is the velocity after half the water has leaked out?

(c) What is the velocity after all the water has leaked out?