Question

why s difficult to write in an smooth surface.

Answer 1

Hey,
Ur answer is here,
this is because smoother the surface lesser the friction and due to this only the pencil lid fails to get a contact on the surface of the smooth paper and that's why why are unable to write on such a paper.
Hope it helps you ☺️

Answer 2

we write due to the friction between surface and pen or chalk

as on smooth surface the friction is veey less ao we cant write