Maharashtra BoardEnglish MediumSTD 12 SciencePhysicsMechanical Properties of Fluids4 Marks
Question
How much work is required to form a bubble of 2 cm radius from the soap solution having surface tension 0.07 N/m.
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Answer
Data $: r =4 cm =4 \times 10^{-2} m , T =25 \times 10^{-3} N / m$ Initial surface area of soap bubble $=0$ Final surface area of soap bubble $=2 \times 4 \pi r^2$ $\therefore$ Increase in surface area $=2 \times 4 \pi r^2$ The work done $=$ surface tension $\times$ increase in surface area $=T \times 2 \times 4 \pi r^2$ $=25 \times 10^{-3} \times 2 \times 4 \times 3.142 \times\left(4 \times 10^{-2}\right)^2$ $=1.005 \times 10^{-3} J$ The work done $=0.07 \times 8 \times 3.142 \times\left(2 \times 10^{-2}\right)^2$ $=7.038 \times 10^{-4} J$
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