A 10 kg block on a horizontal surface is pulled by force F at 30° above the horizontal. If μₛ = 0.25 and g = 10 m s⁻², the force required to just start motion is:
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Question

A 10 kg block on a horizontal surface is pulled by force F at 30° above the horizontal. If μₛ = 0.25 and g = 10 m s⁻², the force required to just start motion is:

G1 Physics · Accepted Answer

At limiting equilibrium: N = mg − F sin 30° = 100 − F/2 Horizontal balance at impending motion: F cos 30° = μₛN (√3/2)F = 0.25(100 − F/2) 4√3 F = 200 − F F = 200/(4√3 + 1) ≈ 25.2 N Hence option B.