A cue ball and an eight ball are at rest on a pool table. You then hit the cue b
ID: 1445996 • Letter: A
Question
A cue ball and an eight ball are at rest on a pool table. You then hit the cue ball so that it is moving horizontally as shown from above. It hits the eight ball and the two balls leave the collision as shown. If the initial time is just before the collision between the two balls, and the final time is just after, answer the following questions.
Which is true about the momentum of the cue ball?
A. There is not enough information to tell.
B. It is NOT conserved.
C. It IS conserved.
Which is true about the momentum of the system containing both the cue ball and the eight ball?
A. There is not enough information to tell.
B. It IS conserved.
C. It is NOT conserved.
An athlete who is initially at rest in a squatted position jumps vertically upward and then lands going back to the original squatted position (ending at rest with the same center of mass height as at the start). The time period I begins just as the athlete starts the upward motion and ends right as her feet leave the ground. The second time period II begins just as the athlete's feet touch the ground upon landing, and ends as soon as she is stationary again in the squatted position. The height of the athlete's center of mass is the same when her feet leave the ground and when they touch upon landing.
Compare the impulse from the normal force of the ground on the athlete for the two time periods.
A. The impulse for period I is equal in magnitude and direction to that for period II.
B. The impulse for period II is larger in magnitude than for period I.
C. The impulse for period I is larger in magnitude than for period II.
D. The impulse for period I is equal in magnitude and opposite in direction to that for period II.
E. More information is needed to compare the impulses.
Explanation / Answer
1. Momentum of CUE ball is conserved.
2. Momentum of the whole system is also conserved
3.
D. The impulse for period I is equal in magnitude and opposite in direction to that for period II.