Question

Why it is easy to write w with a pencil on a paper but not on glass

Answer 1

because paper produce more friction then glass..

Answer 2

Paper produces more friction than glass.A glass is highly polished so it has less friction.Due to this, the pencil glides effortlessly hence it becomes very difficult to write on glass.
In other hand, paper has more friction hence the pencil is able to form impression on the paper.

Hope This Helps You!