Refer to the diagram shown below.
μ = 0.2. the coefficient of dynamic friction
N = mg cosθ, the normal reaction
μN = μmg cosθ, the frictional force resisting motion down the inclined plane.
mg sinθ = the force driving the block down the inclined plane.
Because the block slides down the inclined plane with constant velocity, it is in dynamic equilibrium.
Therefore
mg sinθ = μmgcosθ
tanθ = μ = 0.2
θ =tan⁻¹ 0.2 = 11.3°
Answer: 11.3°
