If the surface tension of a soap solution is $3 \times 10^{-2} \mathrm{~N} / \mathrm{m}$, then the work done…
If the surface tension of a soap solution is $3 \times 10^{-2} \mathrm{~N} / \mathrm{m}$, then the work done in
forming a soap film of $20 \mathrm{~cm} \times 5 \mathrm{~cm}$ will be
$6 \times 10^{-3} \mathrm{~J}$
$6 \times 10^{-4} \mathrm{~J}$
$6 \times 10^{-2} \mathrm{~J}$
$6 \mathrm{~J}$
Solution
$\begin{aligned} W &=2 T \times A \\ &=2 \times 3 \times 10^{-2} \times 100 \times 10^{-4} \\ &=6 \times 10^{-4} \mathrm{~J} \end{aligned}$