1. The problem statement, all variables and given/known data A 2 kg frictionless cart with a velocity of 6 m/s hits a wall and rebounds with a velocity of 4 m/s. What is the impulse on the cart by the wall? Is momentum conserved? 2. Relevant equations J = Δp 3. The attempt at a solution J = Δp = pf-pi = mvf-mvi = 2kg (-4m/s -6m/s) = -20 kgm/s I think I solved the part for the impulse correctly but needed some help with the reasoning for the second part of the question. I think that the momentum would not be conserved in this case because there is an impulse so there's a net force on the system. On the other hand the system is not defined so the momentum can be conserved if the system is considered to be both the cart and the wall, since the wall would experience an impulse from the cart. Which line of reasoning is correct?