Physics - NLM Question with Solution | TestHub

Block does not move upto a maximum applied force of $3 \mathrm{N}$down the inclined plane.

Equation of motion is $3+mg \sin 30°=F$

$3+mg \sin 30°=\mu mg \cos 30°$            ....(i)

Similarly, block also does not move upto a maximum applied force of $12 \mathrm{N}$ up the plane.

Now, equation of motion is

$mg \sin 30°+F=12$

or, $mg \sin 30°+\mu mg \cos 30°=12$           ...(ii)

Solving Eqs. (i) and (ii), we have

$mg \sin 30°=\frac{9}{2}$ and $\mu mg \cos 30°=\frac{15}{2}$

Hence, dividing

$\therefore \frac{1}{\mu }\tan 30°=\frac{9/2}{15/2}=\frac{3}{5}$

$\Rightarrow \mu =\frac{5}{3\sqrt{3}}$