Two centuries after Leonardo's discoveries, the French physicist
Guillaume Amontons considered the problem of friction again. In his
experiments he used springs to measure lateral forces and therefore he must have been able to measure both
static and kinetic friction. However, we must conclude, that also
Amontons wasn't aware of the difference of the two friction phenomena.
Amonton postulated the following friction laws:
|The spring D measures the friction force during the sliding process between materials A and B. Spring C adjusts
the normal force.
Amontons found a material-independent friction coefficient
of 0.33 and therefore
also he believed in the existence of a universal friction
- The resistance caused by rubbing only increases or
in proportion to greater or lesser pressure (load) and not
to the greater or lesser extent of the surfaces.
- The resistance caused by rubbing is more or less
the same for iron,
lead, copper and wood in any combination if the surfaces are
coated with pork
- The resistance is more or less equal to one-third
of the pressure