The first billiard ball collides with a stationary identical billiard ball in an elastic head-on collision. After transferring all of its momentum, which is true of the first ball? a It moves in the opposite direction.
b It has one-half its initial velocity.
c It maintains its initial velocity.
d It comes to rest

Aspring is used to stop a 50-kg package which is moving down a 20º incline. the spring has a constant k = 30 kn/m and is held by cables so that it is initially compressed 50 mm. knowing that the velocity of the package is 2 m/s when it is 8 m from the spring and neglecting friction, determine the maximum additional deformation of the spring in bringing the package to rest.