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    				| 1. | Find the free energy of the surface layer of a mercury droplet of diameter `d = 1.4 mm` , (b) a soap bubble of diameter `d = 6.0 mm` if the surface tension of the soap water solution is equal to `alpha = 45 mN//m`. | 
| Answer» (a) The free energy per unit area being `alpha`, `F = pi alpha d^2 = 3 mu J` (b) `F = 2 pi alpha d^2` because the soap bubble has two surfaces. Substitution gives `F = 10 mu J`. | |