PROBLEMS
The following applies to questions 1-6:
A truck of mass 2m and moving at speed v along the x-direction, crashes into a the rear of a car of mass m while the car is at rest at a stoplight.
1. If neither vehicle has its brakes applied, and if e=0, what will be the velocity (not speed) of the vehicles immediately after collision in E?
2. What is the velocity of the center of mass (in earth frame E) before, during and after the collision in problem number 1?
3. What is the momentum of the system in C before and after the collision?
4. If the same collision takes place with e=0.2, what are the initial velocities of the two vehicles in C?
5. What are the final velocities of the two vehicles in C?
6. What are the final velocities of the two vehicles in E?
7. A ping pong paddle being swung at speed v (assume mass is much larger than the ball) strikes a stationary ball. If e=1, how fast will the ball be moving in E immediately after impact? In C?
8. A tennis ball is thrown against a brick wall that is in the y-z plane. The ball is moving in the x-direction at speed 5 m/s. If e=0.60, what is ball's velocity after impact in E?
9. The same tennis ball (b) in the last problem has an initial velocity of . What is its final velocity if it undergoes a collision with the same e=0.60 as in the last problem. Keep in mind that only the component of velocity perpendicular to the wall is affected during the collision.
10. In parallel to the baseball and bat example problem in the section titled "collisions", find the ball's and the wooden bat's final velocies in E with only one change: Make the ball's initial velocity in E such that it's moving leftward and dropping, or .
ANSWERS
1. 2v/3
2. 2v/3
3. ,
4. v/3 , -2v/3
5. -0.07v, 0.13v
6. 0.60v, 0.80v
7. 2v, v
8. -3m/s
9. -6m/s + 3m/s
10.