Question

The energy required to break a mercury drop of 1cm radius into 1000 small drops of equal size is….Joule (given the surface tension of mercury is $0.4N.m^{-1}$)

• A. $144\pi \times {10}^{-2}$
• B. $1.44\pi$
• C. $14.4\pi \times {10}^{-4}$
• D. $144\pi$

Answer 1

The correct option is C $14.4\pi \times {10}^{-4}$

$T=0.4N{m}^{-1},R=1cm,n=1000;R^3=n{r}^3\Rightarrow r=0.1cm$

Surface energy S$=4\pi R^{2}T$

$S_2=n4\pi r^{2}T;S_1=4\pi R^{2}T$

Work done = $S_2-S_1=4\pi T[n{r}^2-R^2]=4\pi \times 0.4[{10}^3\times {10}^{-6}-{10}^{-4}]$

= $1.6\pi \times {10}^{-4}\times 9=14.4\pi \times {10}^{-4}$ Joule