Finding theta on an incline plane

[jorcrobe]

Homework Statement

A block is resting on a wooden plank. On one end of the plank is a hinge so the other end my be lifted to create and angle θ with respect to the horizontal. The plank has a coefficient of static friction of μs.
Using the sum of forces along the plank. Find the angle at which the block begins to move in terms of μs.

Homework Equations

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The Attempt at a Solution

I gathered that in order for the block to move, the force of static friction must be met, so I set the force of friction equal to the weight force pointing down the slope; thinking that these two must be at least equal for movement. So, I have:

Fw_parallelToSlope = mgsin(theta)
Ff_static = mgcos(theta) * μ

Setting equal to:
mgcos(theta) * μ = mgsin(theta)

(rearranged below for theta)
theta = atan(μ)Thoughts? Thanks, and best wishes.

 

[LawrenceC]

Assuming that atan(mu) is arctan(mu), you've got it correct.