71. Two bumper cars in an amusement park ride collide elastically as one approaches the other directly from the rear (Fig. 7-43 ). Car A has a mass of 435 kg and car B 495 kg, owing to differences in passenger mass. If car A approaches at 4.50 m/s and car B is moving at 3.70 m/s, calculate (a) their velocities after the collision, and (b) the change in momentum of each. MA = MB = 435 kg 495 kg VA = UB= (a) 4.50 m/s 3.70 m/s (b) U'A U B Figure 7-43 Problem 71: (a) before collision, (b) after collision