Question

Energy needed in breaking a drop of radius $R$ into $n$ drops of radii $r$ is given by

• A. $4 \pi T\left(n r^{2}-R^{2}\right)$
• B. $\frac{4}{3} \pi\left(r^{3} n-R^{2}\right)$
• C. $4 \pi T\left(R^{2}-n r^{2}\right)$
• D. $4 \pi T\left(n r^{2}+R^{2}\right)$

Answer 1

Answer: (A)

Energy needed $=$ Increment in surface energy
=( surface energy of $n$ small drops) $-$ (surface energy of one big drop)
$=n 4 \pi r^{2} T-4 \pi R^{2} T $
$=4 \pi T\left(n r^{2}-R^{2}\right)$