Answer: Because The potential energy you build going up the hill can be released as kinetic energy — the energy of motion that takes you down the hill. Once you start cruising down that first hill, gravity takes over and all the built-up potential energy changes to kinetic energy. Gravity applies a constant downward force on the cars.Potential energy is the energy an object has as a result of its position. Potential energy is stored energy that has not yet been released. Gravitational potential energy is potential energy that results from an object's position in a gravitational field, and is equal to the object's weight multiplied by its height.
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