The least potential energy would go at the very bottom of the track. the greatest kinetic energy would be on the upper half of the track and the least kinetic energy would be on the lower half of the track. please review this on google if you are not sure.
Answer: 50 gram superball that strikes the wall at 1 m/s and bounces away at 0.8 m/s has greater change in kinetic energy.
Explanation:
50 gram superball that strikes the wall at 1 m/s and bounces away at 0.8 m/s has the greater change in kinetic energy because the collision is elastic in nature that is bodies separates after collision and doesn't lose any kinetic energy.
Also for an elastic collision, both the momentum and energy of the bodies are conserved compare to inelastic collision where only momentum is conserved but not the kinetic energy(this is attributed to bodies that sticks together after collision).