1. The problem statement, all variables and given/known data This is a conceptual question for a lab. In the lab we used two gliders on a nearly frictionless airtrack on a level surface, with photogates set up to measure the velocities of the two gliders before and after the collisions. The second glider was initially stationary, and the first glider was given an initial velocity and made to collide with the second glider. In one trial, the two gliders had nearly equal mass. Velcro was attached to the ends of the gliders, so when they hit each other, they stuck together afterwards. This was called a perfectly inelastic collision. In lab calculations we proved that in this scenario, momentum of the system was conserved, but the kinetic energy of the system was not conserved. My question is, where does the lost kinetic energy go? 2. Relevant equations p = mv KE = (1/2)mv^2 3. The attempt at a solution I have read about inelastic collisions where the kinetic energy is lost to friction or heat, such as in a car crash for example, where the kinetic energy goes partly into crushing the metal of the cars and into heat. However, in this situation there is no friction. I was thinking maybe the kinetic energy lost goes into vibrational energy in the atoms/molecules of the second glider. I have also read something online that talks about kinetic energy being turned into potential, but how can this be in this case? Thanks!!