MCQ
The minimum value of $‘F’$ so that block is in equilibrium is
  • A
    $2mg$
  • B
    $mg$
  • $mg/2$
  • D
    block cannot be in equilibrium

Answer

Correct option: C.
$mg/2$
c
$\Sigma F_{y}=0$

$\mathrm{N} \cos 60^{\circ}+\mathrm{f}_{\mathrm{max}} \sin 60^{\circ}+\mathrm{F} \sin \theta-\mathrm{Mg}=0 \ldots(\mathrm{i})$ 

$\Sigma F_{x}=0$

$\mathrm{f}_{\mathrm{max}} \cos 60^{\circ}+\mathrm{F} \cos \theta-\mathrm{N} \sin 60^{\circ}=0$            $...(ii)$

$f_{\max }=\mu N$                $...(iii)$

$\frac{\mathrm{d} \mathrm{F}}{\mathrm{d} \theta}=0$         $...(iv)$

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