He Is On The Outside

An engineer, a physicist, and a mathematician are trying to set up a fenced- in area for some sheep, but they have a limited amount of building material. The engineer gets up first and makes a square fence with the material, reasoning that it's a pretty good working solution. "No no," says the physicist, "there's a better way." He takes the fence and makes a circular pen, showing how it encompasses the maximum possible space with the given material. Then the mathematician speaks up: "No, no, there's an even better way." To the others' amusement he proceeds to construct a little tiny fence around himself, then declares: "I define myself to be on the outside."

Friction

Friction annoys me.
It's such a drag.

Discovering Gravity

Physics Teacher: "Isaac Newton was sitting under a tree when an apple fell on his head and he discovered gravity. Isn't that wonderful?"
Student: "Yes sir, if he had been sitting in class looking at books like us, he wouldn't have discovered anything."