Is force of friction always given as `f=mu R`?

Force of friction is measured in:

Force of friction is not a ……….force .

When brakes are applied in a car,the brake-shoes apply frictional force on the wheels.these forces are internal for the system(car).For retardation,external forces ust act on the system.The force of friction at the road surface remains the same before and after teh brakes are applied (f = mu N) .How does the car stop?

Can force of friction on a body be zero even if it is placed on a rough surface?

How can force of friction be reduced ?

The force of friction on a moving object always acts:

What is force of limiting friction and sliding friction?