Mechanical energy nonconservative forces, like frictional forces, will be present, but often they are of negligible values and the mechanical energy's being constant can therefore be a useful approximation. In elastic collisions, the mechanical energy is conserved but in inelastic collisions, some mechanical energy is converted into heat. The equivalence between lost mechanical energy (dissipation) and an increase in temperature was discovered by James Prescott Joule. Many devices are used to convert mechanical energy to or from other forms of energy, e.g. an electric motor converts electrical energy to mechanical energy, an electric generator converts mechanical energy into electrical energy and a
Dalian Dalian Happy Snow World in Ganjingzi District near the airport. Not many people ride bicycles in Dalian because of the hilly roads. Dalian is also one of the many cities in China where there are few motorcycles, because motorcycle riding on most roads is banned by law. The city has a comprehensive bus system and an efficient metro system. As of November 2015, the Dalian Metro consists of the underground Line 1, Line 2, and the overground Line 12 (Formerly called line R2) and Line 3. New lines and expansion of the metro system are under way. The Dalian Tram