Final answer:
A roller coaster reaches peak kinetic energy at its lowest track points due to the conversion of gravitational potential energy into kinetic energy, reflecting the conservation of mechanical energy.
Step-by-step explanation:
A roller coaster has the most kinetic energy at its lowest points during the ride. This is because the gravitational potential energy (PE) the coaster had at the top of the ride is converted into kinetic energy (KE) as the coaster descends.
If work done by friction is negligible, almost all of the initial potential energy is transformed into kinetic energy, resulting in the highest speeds at the lowest points of the track. In physics terms, this is a reflection of the conservation of mechanical energy, where the total mechanical energy (the sum of potential and kinetic energy) remains constant in a closed system.