8.10. Set Up: Use coordinates where is in the direction of the initial motion of A . All motion is along the x-axis. Solve: (a) (b) There is no external force in the x direction so (c) gives (d) kinetic energy is not conserved. Kinetic energy cannot be conserved in a collision where the objects stick together. 8.11. Set Up: Use coordinates where is in the direction of the motion of the ball before it is caught. Figure 8.11 gives before and after sketches for the system of ball plus player. Figure 8.11 Solve: There is no external force in the x-direction, so This gives Reflect: There is a large increase in the mass that is moving so to maintain constant total momentum there is a large decrease in speed. 8.12. Set Up: Let be in the direction the ball is traveling initially. (ball). (you) Solve: (a) gives and (b) gives and 8.13. Set Up: Let be to the right. Solve: (a) says and (b) and Reflect: The total momentum of the system is conserved but the total kinetic energy decreases. 8.14. Set Up:
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