Collision

Consider the simple case of one pool ball colliding head-on with another at rest.  Before the collision, the system's total momentum is the product of the mass of the moving ball and its velocity.  Those of you who have played pool know what happens after such a collision:  the ball that has been moving stops, and the other ball moves forward.  The conservation of momentum can tell us what the speed of that second ball must be.

1. Assuming their masses to be the same, how does the momentum of the second ball after collision compare to that of the first ball before collision? (1)
2. How does the velocity of the second ball after collision, compare to the initial velocity of the first ball? (2)

Consider a wreck in which a car runs into the back of a stationary truck.  Before the collision, the car has momentum forward.  We will suppose that the car and truck stick together after the crash.

The law of conservation of momentum tells us what the momentum of the wreckage will be.

1. What will it be equal to? (1)
2. What values would we need to know to calculate the velocity of the wreckage after impact? (2)