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Mechanical Properties of Fluids — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysicsMechanical Properties of Fluids2 Marks
Question
Find the work done in increasing the radius of a soap bubble from 4cm to 6cm. The value of surface tension for the soap solution is 30 dyne $cm^{-1}$.
✓

Answer

Given, r1 = 4cm, r2 = 6cm, S = 30dyne cm-1 So, change in surface area $=2\times4\pi(6^2-4^2)$ [Shoap solution has two surface]$=8\pi\ 20=160\pi\text{cm}^{2}$
Work done = S × Change in surface area = 30 × 160 × 3.142 = 15081.6erg

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