JEE Main Physics question
The minimum force required to start pushing a body up a rough (frictional coefficient μ) inclined plane is F₁ while the minimum force needed to prevent it from sliding down is F₂. If the inclined plane makes an angle θ with the horizontal such that tanθ = 2μ, then the ratio F₁/F₂ is
Answer: (D)
Solution
F₁ = mg(sinθ+μcosθ), F₂ = mg(sinθ−μcosθ). With tanθ=2μ, writing sinθ=2μcosθ: F₁/F₂ = (2μ+μ)/(2μ−μ) = 3.