there are applications of physics involved when you put pen or pencil to paper. for instance with pencil to paper there tend to me more physics involved. with a pointier tip of the pencil the darker the mark you will make and also the pencil will slide easier considering there is less surface area in contact with the paper. when you put the pencil on paper harder you get darker marks, this is because when you press on the graphite, that force applied is enough to make more grapihe te in contact with the paper. when you have a pen or a badly sharpened pencil you have more resistance being applied on the paper because of the grooves. this is known as friction.