physics help please? multiple choice questions?

[heyheyheythere]

A billiard ball collides with a second identical ball in an elastic head-on collision. What is the kinetic energy of the system after the collision compared with the kinetic energy before the collision?

A. unchanged
B. one-fourth as great
C. two times as great
D. four times as great
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A billiard ball collides with a stationary identical billiard ball in an elastic head-on collision. After the collision, which of the following is true of the first ball?

A. It maintains its initial velocity.
B. It has one-half its initial velocity.
C. It comes to rest.
D. It moves in the opposite direction.
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