# Deriving an equation through a free body diagram

1. Nov 3, 2011

### xgdoyo

1. The problem statement, all variables and given/known data
Use a Free body diagram to show that :Tanθ=static friction, on an incline plane

2. Relevant equations

FF/FN= coeficiant of friction

3. The attempt at a solution
I know I must get an angle to have a tan of the Force of friction and a Normal force, but I don't understant why i need the the angle

2. Nov 4, 2011

### BruceW

You should draw out the free body diagram (since that's what the question asks) and that's usually the best way to go about solving these kinds of questions anyway.

What was the actual question? It would make more sense if it asked you to show that:
$$tan(\theta) \leq \mu_s$$
(where $\mu_s$ is the coefficient of static friction). And remember that the friction force can be less than its maximum possible value, which is why there is an inequality sign.

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