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**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.