Name the force which increases when the two surfaces in contact are made more rough.

Which force gets reduced when the two surfaces in contact are polished to make them smooth?

Why is the surface of a slide polished to make it smooth?

What is the special name of frictional force exerted by fluids (like air or water)?

What is the name of 'special shape' which is given to objects moving through air (or water) to reduce drag?