Final answer:
Friction is the force that takes away some of the cars' total mechanical energy during a roller coaster ride.
Step-by-step explanation:
The force that takes away some of the cars' total mechanical energy during a roller coaster ride is friction. When the roller coaster moves along the track, there is always some level of friction between the car and the track. Friction is a force that opposes motion and acts in the opposite direction, causing a loss of mechanical energy. As the car moves, the friction between the wheels and the track converts some of the mechanical energy into heat, resulting in a decrease in the car's total mechanical energy. Friction is considered a non-conservative force since it does work against the motion of the roller coaster. Therefore, it causes a decrease in the car's mechanical energy as it moves along the track.