Question

The work done in forming a soap bubble of radius 10 cm from soap water of surface tension 35 dyne $c{m}^{-1}$ is (in Joule):

• A. 8800
• B. 8.8 x 10${}^{-3}$
• C. 88
• D. 14000

Answer 1

The correct option is B 8.8 x 10${}^{-3}$

$T=35dyne/c{m}^{-1}$
$=35\times \frac{{10}^{-5}}{{10}^{-2}}N/m=35\times {10}^{-3}N/m$
$SE=2\times 4\pi \times \left({\frac{10}{100}}^2\right)\times 35\times {10}^{-3}$
$=8.8\times {10}^{-3}J$