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
Legend of the Guardians: The Owls of Ga'Hoole "Legend of the Guardians" is the in-flight movie on the aircraft piloted by Carol (Matt Damon), who claims his passengers "... think that $300 and a photo ID gives them the right to fly through the air like the guardian owls of legend!" In a 2014 episode of "The Simpsons", "Specs and the City", Bart considers giving Nelson an "Owls of Ga'Hoole"-themed Valentine, finding it fitting that Nelson should get a Valentine referencing what Bart considers a bad movie. Legend of the Guardians: The Owls of Ga'Hoole Legend of the Guardians: The Owls of Ga'Hoole is a 2010 American-Australian 3D