Question

When a rock is held above the ground, we say it has some potential energy. When we let it go, it falls and we say the potential energy is converted to kinetic energy. Finally, the rock hits the ground. What has happened to the energy?

1) The energy goes to producing sound and to heating the ground, rock, and surrounding air.
2) The rock keeps the energy inside it (saving it for later use).
3) It is lost forever. Energy does not have to be conserved.
4) The energy goes into the ground and, as a result, the orbit of the earth about the Sun is slightly changed.
5) It is transformed back into gravitational potential energy.

Answer 1

When a rock hits the ground, its energy is not lost but converted into heat and sound energy. Energy conservation means the total energy remains constant, but it might change forms and become less useful for practical purposes.

Step-by-step explanation:

When a rock is held above the ground, it possesses gravitational potential energy because of its position relative to the Earth's surface. As the rock is released and falls, its potential energy is converted into kinetic energy. Upon impact with the ground, this energy is not destroyed but transformed into other forms of energy. The correct answer to what happens to the energy when the rock hits the ground is:

1. The energy goes to producing sound and to heating the ground, rock, and surrounding air.

Energy conservation dictates that the total amount of energy in an isolated system remains constant. Therefore, none of the energy is lost; it is simply converted into forms such as sound, heat, and sometimes even slight deformations of the impacted materials, which are usually not recoverable for practical use. The energy certainly does not stay within the rock, alter the orbit of the Earth, or transform back into gravitational potential energy in this context.