I'm having a bit of trouble conceptualizing this. I've looked all over the Internet, and I've been seeing that in completely inelastic collisions the reason that kinetic energy is not conserved is because energy goes into deformation, sound, propelling shrapnel, and especially heat (among other things). I did an experiment with PAScars (which became attached by Velcro upon collision) on a PAStrack, and it was noted that approximately 70% of kinetic energy was lost in the system. At this scale, there's obviously no large deformation of the materials, not a lot of sound or shrapnel propelled out of the system. I can't imagine that the collision of two PAScars buffered by Velcro loses 70% of the energy to heat. Can anyone help me understand this concept?