Problem 1. A ball traveling with an initial momentum of p; = 2.5kg . m/s bounces off a wall and comes back in the opposite direction with a momentum of py = 2.5 kg . m/s. (a) What is the change in momentum of the ball? (b) If the time of collision was 0.15 sec., what was the average force acting on the ball? Problem 2. A railroad car with a mass of my = 12,000kg collides and couples with a second car of mass my = 10, 000 kg that is initially at rest. The first car is moving with a speed of Vi,; = 2.5m/s prior to the collision. (a) What is the initial momentum of the first car? (b) If external forces can be ignored, what is the final velocity of the two railroad cars after they couple