Question 134 of 210

A cubic block of mass $m$ is sliding down on an inclined plane at $60^{\circ}$ with an acceleration of $\frac{\mathrm{g}}{2}$, the value of coefficient of kinetic friction is

A$\sqrt{3}-1$B$\frac{\sqrt{3}}{2}$C$\frac{\sqrt{2}}{3}$D$1-\frac{\sqrt{3}}{2}$

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Answer: (A) $\sqrt{3}-1$

$\mathrm{mg} \sin 60^{\circ}-\mu \mathrm{mg} \cos 60^{\circ}=\mathrm{ma}$
$g \sin 60-\mu g \cos 60=\frac{g}{2}$
$\frac{\sqrt{3}}{2}-\frac{\mu}{2}=\frac{1}{2}$
$\mu=\sqrt{3}-1$