# NEET Physics Mechanical Properties of Fluids Questions Solved

A liquid drop of diameter D breaks upto into 27 small drops of equal size. If the surface tension of the liquid is $\mathrm{\sigma }$, then change in surface energy is

(a) ${\mathrm{\pi D}}^{2}\mathrm{\sigma }$                          (b) $2{\mathrm{\pi D}}^{2}\mathrm{\sigma }$

(c) $3{\mathrm{\pi D}}^{2}\mathrm{\sigma }$                         (d) $4{\mathrm{\pi D}}^{2}\mathrm{\sigma }$

(b)

Work done = $4{\mathrm{\pi R}}^{2}\mathrm{T}\left({\mathrm{n}}^{1/3}-1\right)=4\mathrm{\pi }{\left(\frac{\mathrm{D}}{2}\right)}^{2}\left({\mathrm{\sigma n}}^{1/3}-1\right)\phantom{\rule{0ex}{0ex}}={\mathrm{\pi D}}^{2}\mathrm{\sigma }\left({27}^{1/3}-1\right)=2{\mathrm{\pi D}}^{2}\mathrm{\sigma }$

Difficulty Level:

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