Question

A liquid drop of diameter D breaks upto into 27 small drops of equal size. If the surface tension of the liquid is σ, then change in surface energy is

• A. $\pi D ^ { 2 } \sigma$
• B. $2 \pi D ^ { 2 } \sigma$
• C. $3 \pi D ^ { 2 } \sigma$
• D. $4 \pi D ^ { 2 } \sigma$

Answer 1

Answer: (B)

$2 \pi D ^ { 2 } \sigma$

Answer 2

Work done = $4 \pi R ^ { 2 } T \left( n ^ { 1 / 3 } - 1 \right)$ $= 4 \pi \left( \frac { D } { 2 } \right) ^ { 2 } \sigma \left( n ^ { 1 / 3 } - 1 \right)$

$= 2 \pi D ^ { 2 } \sigma$