Friction

[Dan Squire]

Q:  Why is friction independent of contact surface area?
A:  When dealing with a dry friction problem the force of friction is equal
to the coefficient of friction multiplied by the normal force.  The contact
surface area does not occur  in the equation.  This equation takes a
different form for belt friction.  For example, music wire wrapped around a
hitch pin, capo bar, bridge pin, or tuning pin.  Even in belt friction the
surface contact area does not have an affect the frictional force.

Well, what about the electrostatic forces between the atoms or molecules
where the surfaces are in contact?
It's nice to know about but its utility in this context is rather questionable.

Respectfully,
Dan Squire
University of  Houston