A car at the top of the hill with 200 J of energy, and rolls down a frictionless surface. The isolated system consists of the car, hill, and earth. What happens to the energy of the system as the car moves down the hill?

1- the total energy stays the same but is converted from being stored as kinetic energy into elastic potential energy as it moves.

2- The total energy decreases and is converted from being stored as elastic potential energy into kinetic energy as it moves.

3- The total energy stays the same but is converted from being stored as gravitational potential energy into kinetic energy of the car as it moves

4- The total energy decrease and is converted from being stored as gravitational potential energy into kinetic energy as it moves.

3- The total energy stays the same but is converted from being stored as gravitational potential energy into kinetic energy of the car as it moves

Explanation:

According to the Principle of Energy Conservation, the energy is not created nor destroyed, but transformed. The gravitational potential energy at the top of the hill is transformed into a sum of lower potential energy and kinetic energy due to the absence of non-conservative forces:

The correct answer is 3.

The total energy stays the same but is converted from being stored as gravitational potential energy into kinetic energy of the car as it moves

Explanation:

We know from the principle of conservation of energy that:

"Energy can neither be created nor destroyed, rather it changes from one form to another form".

So clearly, option 2 and 4 are straight wrong since we know that energy remains constant.

Now we have to choose from option 1 and 3.

We know that potential energy is the energy due the position of car and kinetic energy is the energy due the motion of car. Since the car is moving downhill from the top of a hill, the gravitational potential energy (mgh) that was stored due to the position of the car now must be converted into kinetic energy (½mv²) as the car moves downhill.

Therefore, the correct option must be 3.

The total energy stays the same but is converted from being stored as gravitational potential energy into kinetic energy of the car as it moves.