Pile on more spheres and the contact stresses increase, to the point of causing frictional instability (dynamic friction), and perhaps failure.
If this water is removed, by extreme drying, the rock minerals do not behave at all as expected: they exhibit no fault healing or dynamic friction.
PTFE shows one of the smallest coefficients of static and dynamic friction, down to 0.04.
Note that μ can be the coefficient for static or dynamic friction.
For a moment the eyes of the two men locked and it was as if sparks flew from the dynamic friction of the contact.
They are known for their low static friction and highly consistent dynamic friction.
Also, friction values differ in static friction and dynamic friction.
Since it is now sliding across the ground, the friction involved is now dynamic friction.
For most materials, dynamic friction is only half that of static friction.
Efficiency is generally high, because most of the dynamic friction is caused by very slight transitional clutch speed changes.