7 - Friction
Published online by Cambridge University Press: 05 June 2012
Summary
Force of friction
Friction between two solid surfaces is that which tries to prevent one surface from sliding over the other. It is caused by a roughness in the surfaces so that protruding particles which form part of one surface interlock with particles which protrude from the other surface. Such surfaces would quickly wear down if forced to slide over one another. To prevent this, a lubricant oil is used to separate bearing surfaces. However, friction is often an important factor in statics for maintaining equilibrium.
Friction between two dry surfaces is sometimes called Coulomb friction since Coulomb performed many experiments to establish some empirical laws (C.A. Coulomb, Theorie des machines simples, Paris, 1821). However, much was known about friction before then, as may be seen from the information on friction in a physics textbook published in 1740 (Pieter Van Musschenbroek, A treatise on natural philosophy for the use of students in the university, translated into English by John Colson, Lucasian Professor of Mathematics in the University of Cambridge, 2nd edn, London, 1740).
Let us regard friction as being the tangential component of the reaction force, between two surfaces in contact, which tries to prevent sliding. If the force which is trying to produce sliding is gradually increased, friction will increase to maintain equilibrium until a maximum value is reached, after which sliding commences. We shall refer to this maximum value as limiting friction.
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- Statics and Dynamics with Background Mathematics , pp. 98 - 108Publisher: Cambridge University PressPrint publication year: 2003