1. The problem statement, all variables and given/known data One hockey puck of mass 0.2 kg strikes an identical stationary puck on a frictionless ice rink. If the first puck had a velocity V0 = 3.8 m/s before the collision and V1 = 0.8 m/s after in the same direction, what fraction of the energy was lost? 2. Relevant equations Conservation of momentum m1v1 + m2v2 = m3v3 + m4v4 Work energy theorem k = (1/2) mv^2 or (mv)^2/2m 3. The attempt at a solution 3.8 + 0 = .8 + 3 (I left out mass becuase all objects have the same mass.) I am pretty much stuck becuase I do not know the final velocity of V2, and if there was energy lost then V2 shouldn't equal 3 m/s.