Question

way frictional force increase with roughness​

Answer 1

Answer:

friction is the opposite force applied from surface to object.

when the surface is rough then it applies more opposite force.

Answer 2

Explanation:

Depending on the material, the roughness will affect the friction differently. For example in asphaltic roads, initially the roughness is high and over time is decreasing, but the peak maximum friction is reached after some erosion - that is the friction increases a little before it starts to decrease duo to aging effects. You can check some more details in my publication here:

Article Mapping Asphaltic Roads’ Skid Resistance Using Imaging Spectroscopy