Question

Find the value of force $F$, if the tension in the string connecting the $2kg$ block and $3kg$ block is $T=20N$. Consider all surfaces to be smooth.

• A. $100N$
• B. $50N$
• C. $150N$
• D. $200N$

Answer 1

The correct option is D $200N$

FBD of $2kg$ block,

Acceleration is
$a=\frac{F_{net}}{m}=\frac{20}{2}$
$a=10{m/s}^2$

As the blocks are connected by string, they all move with same acceleration.

On applying newton's second law in horizontal direction, we get acceleration of system as
$a=\frac{F}{2\left(M_{\text{sys}}\right)}=\frac{F}{20}{m/s}^2$
$10=\frac{F}{20}$ $(\because a=10{m/s}^2)$
$\Rightarrow F=200N$