as the random motions of the particles that comprise matter. This equivalence between mechanical energy and heat is especially important when considering colliding objects. In an elastic collision, mechanical energy is conserved – the sum of the mechanical energies of the colliding objects is the same before and after the collision. After an inelastic collision, however, the mechanical energy of the system will have changed. Usually, the mechanical energy before the collision is greater than the mechanical energy after the collision. In inelastic collisions, some of the mechanical energy of the colliding objects is transformed into kinetic energy of the constituent particles. This increase in kinetic energy of the constituent particles is perceived as an increase in temperature. The collision can be described by saying some of the mechanical energy of the colliding objects has been converted into an equal amount of heat. Thus, the total energy of the system remains unchanged though the mechanical energy of the system has reduced. Satellite A satellite of mass at a distance from the centre of Earth possesses both kinetic energy, , (by virtue of its motion) and gravitational potential energy, , (by virtue of its position within the Earth's gravitational field; Earth's mass is ). Hence, mechanical energy of the satellite-Earth system is given by If the satellite is in circular orbit, the energy conservation equation can be further simplified into since in circular motion, Newton's 2nd Law of motion can be taken to be Conversion Today, many technological devices convert mechanical energy into other forms of energy or vice versa. These devices can be placed in these categories: An electric motor converts electrical energy into mechanical energy. A generator converts mechanical energy into electrical energy. A hydroelectric powerplant converts the mechanical energy of water in a storage dam into electrical energy. An internal combustion engine is a heat engine that obtains mechanical energy from chemical energy by burning fuel. From this mechanical energy, the internal combustion engine often generates electricity. A steam engine converts the heat energy of steam into mechanical energy. A turbine converts the kinetic energy of a stream of gas or liquid into mechanical energy. Distinction from other types The classification of energy into different types often follows the boundaries of the fields of study in the natural sciences. Chemical energy is the kind of potential energy "stored" in chemical bonds and is studied in chemistry. Nuclear energy