Which of the following is true about magnetic poles?
a. like poles repel each other, and opposite poles attract each other.
b. like poles attract each other, and opposite poles repel each other.
c. like poles attract each other.
d. opposite poles repel each other.

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.