Question

Three blocks $A$, $B$ and $C$ weighing $1kg,8kg$ and $27kg$ respectively are connected as shown in the figure, with an inextensible string and are moving on a smooth surface. If tension $T_3$ is equal to $36N$, then tension $T_2$ is

• A. $18N$
• B. $9N$
• C. $3.375N$
• D. $1.25N$

Answer 1

The correct option is B $9N$

Consider all the blocks connected with inextensible strings as a system.
FBD of the system will be:

From second law, net acceleration of the system,
$a_{net}=\frac{F_{net}}{m_{total}}=\frac{36}{1+8+27}=1m/s^2$

Now FBD of $27kg$ block will be

$36-T_2=m{a}_{net}=27\times 1$
$\Rightarrow T_2=9N$