Question

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

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

Answer 1

Answer: (A)

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