1. The problem statement, all variables and given/known data So this isn't necessairly a direct problem, but we are currently doing a momentum lab in my AP Physics B course and the lab is basically dealing with 4 cases of collision between two carts. In all cases we are to measure the velocity just before collision of the two carts and just after collision. We are using sonic detectors on both sides of the track to do this. In case 1, the carts are collided (they are nearly the same mass) with one cart sitting motionless on the track and the plunger cart hitting it going approx. 3.0 m/s. In case 2, the conditions are the same except an approx 1/2 kg mass is added to the passive cart. In case 3, the carts are the same except they are turned so the velcro sides face each other so they stick together after the plunger cart rams into the passive cart. The fourth case is the same except for the same mass is added once again. 2. Relevant equations None 3. The attempt at a solution We are asked what type of collision is each case, and I have stated it is elastic for case 1 and 2, and completely inelastic in case 3 and 4....... but I don't think this is possible because no collisions are perfectly elastic or inelastic? I may have to ask my instructor on this question... The second question I have is regarding how well my results support the expected results, but I don't know what my expected results should be? Should my momentums be related in some way? Would this be percent error or percent difference? And what key concept is this showing? conservation of momentum?