Please help?

[Luvs_Mariah_C]

A billiard ball traveling at 4.0 m/s has an elastic head-on collision with a billiard ball of equal mass that is initially at rest. The first ball is at rest after the collision. What is the speed of the second ball after the collision?

What equation should i use? Please post.

[Integral]

See this thread (http://www.physicsforums.com/showthread.php?s=&threadid=14097)

[Luvs_Mariah_C]

That shows me the anser, I'm looking for the equation to find the answer myself. Thank you anyways.

[Integral]

Look again.