Question

What is the work done in blowing to from a soap bubble of surface area $40 \, c m^{2}$ ? Take surface tension of the soap solution as $0.03 \, N \, m^{- 1}$ .

• A. $2.4\times 10^{- 4} \, J$
• B. $1.2\times 10^{- 2} \, J$
• C. $3.6\times 10^{- 4} \, J$
• D. $4.2\times 10^{- 4} \, J$

Answer 1

Answer: (A)

Here, surface tension, $S =0.03 \,N m ^{-1}$
Surface area $=40 cm ^2=40 \times 10^{-4} \,m ^2$
Work done $=$ surface tension $\times$ change in surface area
$0.03 \times 240 \times 10^{-4} J =2.4 \times 10^{-4} J$