1. The problem statement, all variables and given/known data A 0.2 kg block, moving at 6 m/s, is catching up and colliding elastically with a 0.6 kg block that is moving along the same line and in the same direction. Find the velocities of the ball after this one-dimensional collision. 2. Relevant equations Conservation of momentum, conservation of energy 3. The attempt at a solution First, I figured the momentum and kinetic energy would be conserved so I setup a couple of equations: m1v1i + m2v2i = m1v1f + m2v2f and m1v1i^2 + m2v2i^2 = m1v1f^2 + m2v2f^2 At this point, I realize I have 3 unknowns (v2i, v1f and v2f) and I simply don't know what I can even do with this information. Any ideas at all would be helpful.