The problem statement, all variables and given/known data 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?