Question

A water drop of radius 1mm is split into ${10}^6$ identical drops. Surface tension of water is 72 dynes/cm. Find the energy spent in this process.

Answer 1

Initial volume $=$ Final volume

$\Rightarrow \frac{4}{3}\pi (1{)}^3={10}^6\frac{4}{3}\pi r^3$

$\Rightarrow {10}^{-6}=r^3$

$\Rightarrow r={10}^{-2}mm$

$\Rightarrow r=10\mu m$

Initial surface area $=4\pi 1^{2}m{m}^2$

Final surface area $={10}^{6}4\pi {10}^{-4}m{m}^2$

$△A=99\left(4\pi \right){10}^{-2}c{m}^2$

Workdone $=T\times △A=895.2768dyne$