1. The problem statement, all variables and given/known data mass of Fuzzy = 100.0kg mass of cart = 200.0kg 2. Relevant equations Conservation of Momentum for 1D Motion Relative Velocity for 1D Motion 3. The attempt at a solution Since everything is at rest at the beginning, the total momentum of the system is 0. So at the end, 0 = m1v1 + m2v2 --> m1v1 = -m2v2, so m1v1 = -m(5+v1), and after expanding that, and solving for v1, the answer isn't correct. The correct answer is 0.685m/s [N]. IS my approach wrong? I think it might be do to a change in the mass of the system, but even if that is the right way to go, I don't know how to incorporate that in the equation.