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 from the horizontal such that tan θ = 2 μ, then the ratio F₁/F₂ is

(a) 4

(b) 1

(c) 2

(d) 3

Answer 1

 Correct option (d) 3
  Explanation:

F₁  = mg (sinθ + μcosθ ) [as body just in position to move up, friction force downward]
F₂ = mg(sin θ - μcosθ ) [as body just in position to slide down, friction upward]