Question

Find the magnitude & direction of frictional force between block A and table, if block A is pulled towards left with a force of $50N$.

• A. $10\hat{i}$
• B. $10\hat{j}$
• C. $20\hat{i}$
• D. $20\hat{j}$

Answer 1

The correct option is A $10\hat{i}$

Maximum possible frictional force on block A , $f=\mu N=\mu mg=0.8\left(5\right)\left(10\right)=40N$...(i)
Considering frictional force is sufficient to prevent movement of blocks i.e. $a=0$
writing equilibrium equation for block A
$50-f-T=0$...(ii) where $f$ is friction force and $T$ is the tension in the rope.
Writing equilibrium equation for block B
$T=4g=40N$...(iii)
using equation (ii) and (iii) $\Rightarrow f=1g=10N$
the frictional force value is less than the maximum limit of friction force hence the system is in static condition.