Please please help!! 3.) A frustrated tennis star hits a ball straight up into the air at 22.8 m/s.
How long before the ball hits the ground? How high did the ball go?
4.) What is the velocity of the ball in #3 right before it hits the ground?

In a game of pool, ball a is moving with a velocity v0 of magnitude v0 = 15 ft/s when it strikes balls b and c, which are at rest and aligned as shown. knowing that after the collision the three balls move in the directions indicated and assuming frictionless surfaces and perfectly elastic impact (that is, conservation of energy), determine the magnitudes of the velocities va, vb, and vc.