Friction is an opposing force that acts between two bodies having relative motion or trying to move relatively. It acts at the contact surfaces of two bodies and opposes their relative motion.
Types of Friction: Friction can be classify into following two types:-
a) External Friction: This type of friction arises when two bodies which are in contact with each other moves relatively or tries to move. The external friction is also called contact friction. External friction is further divided into three types:-
- Static friction
- Limiting friction
- Kinetic friction.
b) Internal Friction: This type of motion arises on account of relative motion between every two layers of a fluid.
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.
Limiting friction: It is the maximum opposing force that comes into play, when one body is just at the point to move over the surface of another body.
Kinetic or Dynamic friction: It is the opposing force that comes into play when one is actually moving over the surface of another body.