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**Homework Statement**

Part one: A block is at rest on an inclined plane whose elevation can be varied. The coefficient of static friction is μs= 0.390, and the coefficient of kinetic friction is μk= 0.190. The angle of elevation θ is increased slowly from the horizontal. At what value of θ does the block begin to slide (in degrees)?

(Hint after getting it incorrect: mass*acceleration = sum of net forces in one direction. Use mu_s to calculate the frictional force for the moment when it starts to slide)

Part two: Evaluate the acceleration of the block.

**The attempt at a solution**

So,

Ff = μFn

Fn= mgcosθ

Fparallel = mgsinθ

Ff = μ(mgcosθ)

When the block begins to slide, the force of friction has to be equal to the force parallel, right? You have to overcome the static μ.

So,

Fparallel = Ff

mgsinθ = μmgcosθ

mg's would cancel, so

sinθ = μcosθ

sinθ/cosθ = μ

tanθ = μ

θ= tan^-1(0.390)

However, the answer I get is 0.372°, and that isn't correct.

For the second half,

ƩFnet = ma

Fparallel - Ff = ma

mgsinθ - mgcosθ = ma

gsinθ - gcosθ = a

There's a flaw in my method, I just don't know what it is. Anyone know how to help?