This is defined as the resistance that one surface offers to its movement over another surface. Friction is a force which acts at the surface of separation of two bodies in contact and tends to oppose the motion of one over the other.
The amount of friction depends upon the nature of the two surfaces and the forces that hold them together.
ADVANTAGES OF FRICTION
It makes the wheels (tyres) of an automobile grip the road to prevent slipping
It makes the brakes of moving cars, bicycles, etc., slow down and stop when necessary.
It alloys conveyor belts turn on pulleys without slipping off.
It facilitates the fastening of a nailinto wood.
It helps in lighting of a match.
The friction between our feet and the floor makes it possible for us to walk.
Friction in Walking
Friction in Car Wheel
DISADVANTAGES OF FRICTION
Friction causes wear and tear of moving parts.
It causes dullness of cutting edges, especially cutting tools like knife, chisel, etc.
It produces heat which may cause damage to machine parts.
It reduces the efficiency of machines.
METHODS OF REDUCING FRICTION
By using ball or roller bearings on solid surface.
By lubricating parts with oil.
By smoothing or polishing the surface.
By streamlining the body which is to move over another body or surface.