Pure Rolling — Incline ConditionHardQuestion 30352
Question
For a sphere (k = 2/5) to roll without slipping down an incline of angle θ, the minimum coefficient of static friction required is:
- A(2/7)tanθCorrect
- B(5/7)tanθ
- C(2/5)tanθ
- Dtanθ/2
Correct answer
(2/7)tanθ
Explanation
For rolling without slipping: friction f = Ma × (k/(1+k)) and N = Mg cosθ. μ_min = f/N = [(k/(1+k)) × g sinθ] / (g cosθ) = (k/(1+k))tanθ = (2/5)/(1+2/5) × tanθ = (2/5)/(7/5) × tanθ = (2/7)tanθ.