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Question 30287
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Laws of Motion and Friction: Advanced — Minimum Force to Slide MCQ

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Advanced — Minimum Force to SlideHardQuestion 30287

Question

What minimum force F applied at angle α to the horizontal will just move a block (mass m, μₛ = μ) on a horizontal surface?
  1. A
    μmg
  2. B
    μmg/cosα
  3. C
    μmg cosα/(1+μ sinα)
    Correct
  4. D
    mg(μ cosα − sinα)

Correct answer

μmg cosα/(1+μ sinα)

Explanation

N = mg − F sinα. At limiting: F cosα = μN = μ(mg − F sinα). Solving: F = μmg/(cosα + μ sinα). Minimize w.r.t. α: optimal α = arctan(μ).

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