Kinetic energy is contained in a moving object, while potential energy exists in a stored form. Potential energy can be changed into kinetic energy. Potential energy is ready for release, while kinetic energy is already doing work. The property of a body determines the type of energy it contains.
Potential energy affects objects within its environment only when it is transformed into other forms of energy. A rock resting on top of a cliff is an example of a body with potential energy. When it falls, it contains kinetic energy. Energy stored in a body due to its elevation is called gravitational potential energy. Some bodies, such as waterfalls, contain both kinetic and potential energies. The height of a waterfall is the basis for its potential energy, while its water movement provides its kinetic energy.
The law of the conservation of energy states that energy does not multiply or disappear and cannot be destroyed. Unlike potential energy, kinetic energy can be transferred from one body to another when the two bodies collide. Energy is a physical quantity because it is proportionate to the mass of an object. The ability of a body to exert pushes and pulls against natural forces such as gravity identifies its type of energy.