Answer the multiple-choice questions below.

1.

17. 30 Car 1 20 Position (m) 10 0- Car 2 -10+- O 0.5 1.0 Time (s) Two identical cars, car 1 and car 2, are moving in opposite directions on a straight road. The position of each car as a function of time is represented in the graph. What is the speed of the center of mass of the two-car system? (A) Zero (B) 10 m/s (C) 20 m/s (D) 40 m/sTwo identical objects, X and Y, move toward each other at different speeds on a horizontal surface with negligible friction, as shown in the top gure. The objects then collide elastically and move away from each other. The kinetic energy of object X as a function of time is shown in the graph. Which of the following is true of speed Vy of object Y? A. UY After the collision is greater than it was before the collision. B. UY After the collision is equal to what it was before the collision. C. UY After the collision is less than it was before the collision. D. UY After the collision cannot be compared to what it was before the collision without knowing the mass of the objects. 0\".ch ObbctY 34. In trial 1 of an experiment, a cart moves with speed vo on a frictionless, horizontal track and collides elastically with another cart that is initially at rest. In trial 2, the setup is identical except that the carts stick together during the collision. How does the speed of the two-cart system's center of mass change, if at all, during the collision in each trial? Trial 1 Trial 2 (A) Does not change Does not change B) Does not change Decreases (C) Decreases Does not change (D) Decreases Decreases