1. The problem statement, all variables and given/known data My teacher explained to my class that Normal force equals Force of Gravity. Given a free body diagram on a flat surface, Normal force is directed up, and Force of Gravity is directed down. 2. Relevant equations So my teacher did the following: Fg = Force of gravity Ff = force of friction Fn = normal force u = co-efficient of friction _________ Ff = uFn Ff = uFg Ff = u*m*g (mass times gravity) How is this possible? normal force is equal to the force of gravity? but they oppose each other, don't they? Thank you so much for any help at all.