“Friction is a necessary evil” – A very famous quote
Friction is the force that opposes the motion of an object that is in contact with another body. The contact is important, since friction is a contact force.
The cause of friction is a combination of several surface phenomena including irregularities in surfaces, Electrostatic force of attraction etc.
Frictional force are of 2 types:
- Static friction
- Kinetic friction
The friction that keeps the body in rest even if enough force is applied. This force has a limit. This limit is called the Maximum static friction or the limiting friction.
The formula for limiting static friction is:
Where N is the normal reaction on the body and µs is the coefficient of static friction.
Where α is the angle of the inclined plane. Now the value of friction for different situations is as follows
When the body is in restfs = mg x sin (α)
The maximum static friction or the limiting friction isfmax = µs x N
When the body starts to slide down the inclined plane the kinetic friction acting on the body is given by
These are the general properties of friction.