If work done in increasing size of a soap film from 10, cm×6, cm to 60, cm×11, cm is 2×10^{-4}, J

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9-1.Fluid Mechanics

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If work done in increasing the size of a soap film from $10\, cm\times6\, cm$ to $60\, cm\times11\, cm$ is $2\times10^{-4}\, J$. What is the surface tension ?

A

$2\times10^{-8}\, Nm^{-1}$

B

$2\times10^{-2}\, Nm^{-1}$

C

$2\times10^{-4}\, Nm^{-1}$

D

none of these

Solution

Work done $=$ Increase in surface area $\times$ Surface tension

$2 \times 10^{-4}=\frac{2(60 \times 11-10 \times 6) \times \mathrm{T}}{100 \times 100}$

$\mathrm{T}=\frac{2 \times 10^{-4}}{2 \times 6 \times 10^{-2}}=\frac{1}{6} \times 10^{-2} \mathrm{\,Nm}^{-1}$

Standard 11

Physics

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