Editing Conservative force (section)

==Non-conservative force==

Despite conservation of total energy, non-conservative forces can arise in classical physics due to neglected [[degrees of freedom (physics and chemistry)|degrees of freedom]] or from time-dependent potentials.<ref>Friedhelm Kuypers. Klassische Mechanik. WILEY-VCH 2005. Page 9.</ref>  Many non-conservative  forces may be perceived as macroscopic effects of small-scale conservative forces.<ref name="Tom">Tom W. B. Kibble, Frank H. Berkshire. Classical mechanics. (5th ed).  Imperial College Press 2004 {{ISBN|1860944248}}</ref> For instance, friction may be treated without violating conservation of energy by considering the motion of individual molecules; however, that means every molecule's motion must be considered rather than handling it through statistical methods. For macroscopic systems the non-conservative approximation is far easier to deal with than millions of degrees of freedom.

Examples of non-conservative forces are [[friction]] and non-elastic material [[stress (mechanics)|stress]]. Friction has the effect of transferring some of the energy from the large-scale motion of the bodies to small-scale movements in their interior, and therefore appear non-conservative on a large scale.<ref name="Tom" /> [[General relativity]] is non-conservative, as seen in the [[Tests of general relativity#Perihelion precession of Mercury|anomalous precession]] of Mercury's orbit.{{citation needed|date=May 2021}} However, general relativity does conserve a [[stress–energy–momentum pseudotensor]].