Question

Find the minimum value of $F$ for which the system is in equilibrium? $[$ Take $g={\text{10 m/s}}^2]$

• A. $30\text{N}$
• B. $10\text{N}$
• C. $15\text{N}$
• D. $20\text{N}$

Answer 1

The correct option is A $30\text{N}$

By FBD of the blocks

As the system is in equilibrium and the $5\text{kg}$ block will have the frictional force $f$ in the backward direction as the block has the tendency to move forward

$T=4g$ $f=\mu mg$
$F+f=T$ $\Rightarrow 4g=F+0.2\left(5\right)g$
$\therefore F=4g-0.2\left(5\right)g=30\text{N}$

Hence option A is the correct answer