SmithPhysletsChap8

Illustration 1: The longer you apply a force to a mass the greater the final momentum will be. As seen in the illustration the mass had an increasing momentum the longer the force was being applied and it finally peaked when the applied force ended.

Illustration 2: The longer a force is applied to a mass the greater it's acceleration and velocity will be. When you stop applying the force on the mass the mass will still travel the same velocity as when you last were applying the force.

Illustration 3: a) When the two balls collide in the elastic collision the momentum and energy is conserved so they travel in the opposite directions. They also end up with the same final velocity as they started since they both had the same initial velocity.

b) The balls start to travel towards each other while decelerating and at the end they reverse back and head the direction opposite of their initial velocity. Therefore, they have backspin.