What is friction ? Explain static frictional force is caused due to roughness of force at microscopic level.

Explanation

Whenever there is relative motion between two surface the force due to l which relative motion is retarded is called frictional force.
As shown in figure an object is placed on horizontal surface

Weight and normal force balance each other
Let horizonatal force force F is applied to object
`mu_(s )` is unitless and dimensionless Ratio of maximum static friction and normal force is called co - efficient of static frcition.
Its value is in range of 0.01 to 1.5
if object does not move than `f_(s) gt mu_(s ) N.`