Friction

Article By:

Barger, Vernon D. Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin.

Last reviewed:April 2020

DOI:https://doi.org/10.1036/1097-8542.272600

Show previous versions

• Friction, published June 2014:Download PDF Get Adobe Acrobat Reader

Resistance to sliding, a property of the interface between two solid bodies in contact. Many everyday activities like walking or gripping objects are carried out through friction, and most people have experienced the problems that arise when there is too little friction and conditions are slippery. However, friction is a serious nuisance in devices that move continuously, like electric motors or railroad trains, since it constitutes a dissipation of energy, and a considerable proportion of all the energy generated by humans is wasted in this way. Most of this energy loss appears as heat, while a small proportion induces loss of material from the sliding surfaces, and this eventually leads to further waste, namely, to the wearing out of the whole mechanism. Almost all the frictional energy appears as heat at the interface between the sliding surfaces. This frictional heat was used by humans in prehistoric times to light fires, and this use survives today in the striking of matches, with chemical combustion initiated by the temperature rise produced by sliding (Fig. 1). However, frictional heat usually is a nuisance, and sliding surfaces must often be cooled to prevent heat damage. Friction is studied in the field of tribology—the science of interactive surfaces in relative motion—which also studies lubrication and wear. See also: Tribology; Wear; Work

The content above is only an excerpt.