Fig, shown a thin film supporting a small weight = `4.5xx10^(-2)N`. What is the weight supported by a film of the same liquid at the same temperature in fig. explain your answer physically.

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Explanation

(a) Here, length of the film supporting the weight = 40cm =0.4 m
Total weight supported (or force) =`4.5xx10^(-2)N`,
Film has two surfaces, `:.`Surface tension, `S = (4.5xx10^(-2))/(2xx0.4) = 5/625xx10^(-2)Nm^(-1)`
Since the liquid is same for all the cases(a), (b) and (c),and temperature is also same, therefore, surface tension for cases (b) and (c) will also be the dame = `5.625xx10^(-2)`. in fig., length of the film supporting the weight is also the same as that of (a), hence the total weight supported in each case is `4.5xx0^(-2)N`.