What is friction
It is a force which opposes motion of one object over another object in contact with it
In easy language,it is a force which makes moving object stop
Example 1
A ball which is moving comes to rest after some time
This is due to force of friction between ball and ground
Example 2
Boat comes to rest if we stop rowing
This is because of the force of friction between water and the boat
What is direction of force of friction?
Friction always acts in the opposite direction of motion
If we push a book on table from left to right
Force of friction moves in opposite direction from right to left
Similarly, if we push a book on table from right to left
Force of friction moves in opposite direction from left to right
What causes friction?
If we take a microscope and zoom in the surface of two objects,
we see that both the surface have some irregularities
When we try to move the object, the irregularities gets interlocked. This causes friction
So,
rougher the surface, more the irregularities. Hence, more friction
smoother the surface, less the irregularities. Hence, less friction
