Question

A soap bubble of radius 2 cm explodes. If the surface tension of soap water is 40 dyne cm${}^{-1}$, the energy released is ..... Joule.

• A. 1280$\pi$ x 10${}^{-7}$
• B. 1280
• C. 12800
• D. 128

Answer 1

The correct option is A 1280$\pi$ x 10${}^{-7}$

Since bubble explodes final radius will be zero
so energy released will be
$2\times 4\pi r^2\times T$
= $2\times 4\pi 2^2\times T$
= 1280 $\pi$ erg
we know that ${10}^7$erg = 1 J
so, 1280 $\pi$ erg = 1280 $\pi \times {10}^{-7}$ J