potential energy (U)
Potential energy, expressed in science as U , is energy that is stored within an object, not in motion but capable of becoming active. When at rest, every object has rest mass potential energy; if the object is in a position to be affected by gravity and to fall, it has gravitational potential energy. Once an object is in motion, potential energy is converted to kinetic energy , which is the energy of motion.
There are a number of kinds of potential energy. The pendulum of a clock, at the top of its swing, has gravitational potential energy which is converted to kinetic energy as it falls. Elastic potential energy is present in an object that can be stretched out and rebound, like an elastic. The potential energy is stored when an elastic is stretched, and converted to kinetic energy when the elastic is released. Other types of potential energy include chemical, which is related to the formation of chemical bonds and electrical, expressed as voltage .