A 40 g marble moving at 2.3 m/s strikes a 29 g marble at rest. Assume the collision is perfectly elastic and the marbles collide head-on. What is the speed of the first marble immediately after the collision? What is the speed of the second marble immediately after the collision?

How do you set this up?

2 answers

two equations: Conservation of momentum
M1V1+m2(0)=M1V1' + m2V2'
solve for v2' in terms of all others.
second equation: conservation of energy
M1V1^2+0=M1V1'^2 + m2V2'^2
put the v2' equation into that equation, and solve for v1'

A bit of algebra is required, get a pad of paper.
I tried plugging the number in and it didn't work...where are the numbers supposed to be placed in the first equation?