1. The problem statement, all variables and given/known data When two carts collide, is momentum conserved at each instant before, during and after the collision? If the carts are of equal mass what happens to their individual momenta during and after the collision? 2. Relevant equations 3. The attempt at a solution I'm actually unsure of what the question means. "If the carts are of equal mass what happens to their individual momenta during and after the collision?" During the collision? I'm confused because we normally just consider before the collision and after the collision, leaving out the complex in-between stuff. As for after the collision, I think the answer is this. If cart 1 is moving at a velocity v relative to cart 2, and cart 2 is at rest, then after the collision, cart 1 will have 0 final momentum relative to cart 2, and cart 2 will have the same initial momentum that cart 1 had. Please correct me if I'm wrong.