Comparing the coefficient of static friction and coefficient of kinetic friction?

Question

How does the coefficient of static friction compare with the coefficient of kinetic friction for the same surfaces, areas and normal force?

Answer 1

static friction > kinetic friction. Reason is that after body is in motion some wear occurs which reduces the contact area in the case of dry friction.

In the case of wet friction a wedge of liquid forms after the motion which floats the moving body thereby reducing fiction.

Answer 2

The answerer above me used the word 'always' that I'm not sure of. When I was at school, I learnt the formula:

mu(s) >/= mu(k) where mu(s) and mu(k) stand for static and kinetic friction respectively.

The formula shows that static friction can be greater or equal to kinetic friction.

The thing that is ALWAYS greater than kinetic friction is called the 'Limiting Friction'.

Answer 3

The coefficient of static friction is -always- larger than the coefficient of kinetic friction. (Unless it's a truly 'frictionless' surface in which case they're both zero)

Doug