Question

In the figure as shown two blocks are connected by a string over a pulley.

Calculate the total work done by tension force on the system for $1\text{m}$ distance covered.

• A. $\frac{80}{3}\text{N}$
• B. $-\frac{80}{3}\text{N}$
• C. Zero
• D. None

Answer 1

The correct option is C Zero

Drawing FBD of the system.


$\therefore$ Applying $2^{nd}$ law, on both the blocks

$T-2g=2a\Rightarrow T-20=2a...\left(i\right)$
$40-T=4a...\left(ii\right)$

We get tention $\left(T\right)$
$\Rightarrow T=\frac{80}{3}\text{N}$
Work done by $T$ for $4\text{kg}=\overrightarrow{F}.\overrightarrow{d}$

$W_{4kg}=-\frac{80}{3}N$. Here the work done is negative as $T$ and displacement are in opposite direction $\overrightarrow{d}$

Work done by $T$ for $2\text{kg}$ = $\frac{80}{3}\text{N}$
$\therefore$ Total work done by the tension is = $-\frac{80}{3}+\frac{80}{3}=0$
Hence option C is the correct answer