Potential Energy

If you lift an object you have to do work on it. This means that energy is transferred to the object. But where is this energy? This energy is stored in the object and is called potential energy. The reason it is called potential energy is because if we let go of the object it would move.

As an object raised above the ground falls, its potential energy is released and transformed into kinetic energy. The further it falls, the faster it moves, as more of the stored potential energy is transferred into kinetic energy. Remember, energy is never created nor destroyed, but merely transformed from one type to another. In this case the potential energy is lost but an equal amount of kinetic energy is gained.

In the example of a falling mass the potential energy is known as gravitational potential energy as it is the gravitational force exerted by the Earth which causes the mass to accelerate towards the ground. The gravitational field of the Earth is what does the work in this case.

Another example is a rubber band. In order to stretch a rubber band we have to do work on it. This means we transfer energy to the rubber band and it gains potential energy. This potential energy is called elastic potential energy. Once released, the rubber band begins to move and elastic potential energy is transferred into kinetic energy.