1. The problem statement, all variables and given/known data Let two particles of collide in a perfectly elastic collision. Particle 1 has a mass of 2m, while particle 2 has a mass of m. Particle 1 has initial velocity v, directed to the right, while particle 2 is at rest. What are the final velocities, v1 and v2, of particle 1 and particle 2? 2. Relevant equations Conservation of Momentum m1v1+m2v2=m1v3+m2v4 Conservation of Energy (1/2)mv1^2+(1/2)mv2^2=(1/2)mv3^2+(1/2)mv4^2 3. The attempt at a solution I'm not sure what to do. I've been messing around with stuff, but I can't seem to get the right answer, and I'm running out of answers on my online homework. I know you have to solve in one equation, and then substitute to the other in order to get down to a workable amount of variables, but I'm not entirely sure how. I"m pretty sure the answer has to be in the form of (constant)v, to show the ratio of the initial velocity that each object was left with, and I just don't know how to whittle it down to that.