Final answer:
The glider's kinetic energy is lower after an inelastic collision compared to before, despite the momentum potentially increasing due to Newton's third law of motion.
Step-by-step explanation:
The form of mechanical energy that is different for the glider before the collision than after the collision is kinetic energy. The collision discussed in the texts provided is inelastic, which means that some of the kinetic energy is not conserved and is instead dissipated as heat, sound, or other forms of non-mechanical energy. Therefore, the glider's kinetic energy after the collision is less than before. When considering an inelastic collision, it is important to note both kinetic energy and momentum. While kinetic energy decreases, the momentum may actually increase due to the interaction between the colliding objects, as described by Newton's third law of motion.