Contact area: Difference between revisions

[[File:Contact.png | thumb | right | Objects ''A'' and ''B'' touching at contact area ''S'']]When two [[Physical body|objects]] touch, only a certain portion of their surface areas will be in contact with each other. This area of true contact, most often constitutes only a very small fraction of the apparent or ''nominal''Contact contact area. In relation to two contacting objects, the '''contact refersarea''' tois the fractionpart of thisthe nominal area that consists of the [[atom]]s of one object being in true contact with the atoms of the other object. Because objects are [[asperities|rarelynever perfectly flat due to [[Asperity (material science)|asperities]], the actual contact area (on a [[microscopic]] scale) is usually much less than the contact area apparent on a [[macroscopic]] scale. Contact area may depend on the [[normal force]] between the two objects due to [[deformation (engineering)|deformation]]. <ref>{{cite journal| last1=Zhai| first1=C.| last2= Hanaor |first2=D. |last3=Proust| first3=G.| last4=Gan| first4=Y.|title= Stress-Dependent Electrical Contact Resistance at Fractal Rough Surfaces| journal= Journal of Engineering Mechanics| year=2015| volume=143|issue=3| pages=B4015001 | url= https://www.researchgate.net/publication/277981414| doi= 10.1061/(ASCE)EM.1943-7889.0000967}}</ref>

It is an [[empirical]] fact for many [[materials]] that ''F ''&nbsp;= &nbsp;''μN'', where ''F'' is the [[friction|frictional force]] for [[sliding friction]], ''μ'' is the [[coefficient of friction]], and ''N'' is the [[normal force]]. There isn't a simple derivation for sliding friction's independence from area.