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 Metro Dalian Metro The Dalian Metro or Dalian Subway is a rapid transit system in the city of Dalian, Liaoning, China. The metro opened on 1 May 2003. The system currently in operation consists of 4 lines: Line 1, Line 2, Line 3, and Line 12. Line 1, opened in 2015 currently in operation, connects east southeast central Dalian with north Dalian. The total length is 28.34 kilometers, with 22 underground stations. Line 2, opened in 2015 currently in operation, connects east central Dalian with west central Dalian. The total length is 42.56 kilometers, with 29 underground stations. The line is