Larry Fine asked: > I'm surprised to hear that friction is independent of the contact area. > Could you please explain why this should be so, counter-intuitively? > An intuitive explanation of this may be had by thinking of the molecular forces which cause friction. Consider static friction, which applies when there is no relative motion between 2 surfaces. On a very small scale the surfaces appear very bumpy and where the bumps coincide the contact area is `cold-welded'. It is these bonds which must be broken to break the frictional contact between the surfaces. The minimum force required to break these bonds is independent of how many there are i.e. the surface area of contact. [Intuitive reasoning only here as requested.] Stephen Birkett (Fortepianos) Authentic Reproductions of 18th and 19th Century Pianos Waterloo, Ontario, Canada tel: 519-885-2228 fax: 519-763-4686
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