(1) Static friction : The opposing force that comes into play when one body tends to move over the surface of another, but the actual motion has yet not started is called static friction.
2) Limiting friction: If the applied force is increased, the force of static friction also increases. If the applied force exceeds a certain (maximum) value, the body starts moving. This maximum value of static friction upto which body does not move is called limiting friction.
FI R or FI = sR
s = FR
Not depend upon
The magnitude of limiting friction between any two bodies in contact is directly proportional to the normal reaction between them.