Question

here the car is dramatically slowed down while not gaining height. what caused the car to slow down?
kinetic energy becomes potential energy.
kinetic energy is destroyed by the brakes in the track.
kinetic energy is converted into thermal energy (heat) via brakes in the track

Explanation:

According to the law of conservation of energy, energy cannot be created or destroyed, only converted from one form to another. Since the car is not gaining height (so no conversion to gravitational potential energy), when it slows down (kinetic energy decreases), the kinetic energy is converted into another form. Brakes involve friction, and friction converts kinetic energy into thermal energy (heat). The first option is wrong as there's no height gain (no potential energy increase). The second option is wrong as energy isn't destroyed.

Answer:

Kinetic energy is converted into thermal energy (heat) via brakes in the track.