Question

For the arrangement shown in figure, the tension in the string to prevent it from sliding down is

• A. $6\text{N}$
• B. $64\text{N}$
• C. $0.4\text{N}$
• D. None of these

Answer 1

The correct option is D None of these

Since $\mu =0.8=\frac{4}{5}$
$\Rightarrow$ Angle of repose $\alpha ={39}^{\circ }$
Since angle which incline makes with the horizontal is ${37}^{\circ }(<{39}^{\circ })$, so the block will not slide down the incline and friction between the block and the incline will be static in nature. So,
$f_s=F_{applied}=mg\sin \left({37}^{\circ }\right)$

Now, if $T$ be the tension in the string, then
$T+f_s=mg\sin \left({37}^{\circ }\right)$
$\Rightarrow T=0$ $\{\because f_s=mg\sin ({37}^{\circ }\left)\right\}$
Hence, the correct answer is (d).