"Don't Let It Fall!"

Molly Wellinghoff

Contrived

"Don't Let It Fall"

 

This picture shows a physics book in static equilibrium. It is in equilibrium because there are four forces acting on the book and they all sum up to equal zero. Gravity is pulling the book down with a force of the book's mass times gravity (F=mg). The hand is also exerting a force on the book directed towards the wall. According to Newton's third law, every action has an equal and opposite reaction. This means that the wall has to exert a force of the same size in the opposite direction. The wall's force is directed towards the hand and it is called the normal force (Fn). Friction is the upward force which prevents the book from slipping. Friction is found by multiplying the coefficient of friction and the normal force. The coefficient of friction is determined by the interaction of the two surfaces with each other. In this case, the normal force is large, so the friction force is enough to prevent the book from slipping down the wall.

Done