In a Perfectly Elastic Collision, a 400-G Ball Moving

Short Answer

In a perfectly elastic collision, a 400-g ball moving toward the east at 3.7 m/s suddenly collides head-on with a 200 g ball sitting at rest.
(a) Determine the velocity of the first ball just after the collision.
(b) Determine the velocity of the second ball just after the collision.
(c) Is kinetic energy conserved in this collision? How do you know?