Principle of Conservation of Energy

Energy is the capacity to do work.Energy is a scalar quantity. The SI unit for energy is the joule.The energy of systems with mass are kinetic energy and gravitational potential energy. Potential energy is stored energy.The principle of conservation of energy states that the total energy of a closed system remains constant. Energy cannot be created or destroyed but can be transferred from one form to another and from one object to another.Perpetual motion is impossible on Earth because work must be done against air resistance or friction and energy will eventually be transferred to the thermal energy of the surroundings.