A certain number of spherical drops of a liquid of radius r coalesce to form a single drop of radius R and volume V. If T is the surface tension of the liquid, then (a) energy = 4VT (1/r - 1/R) is released. (b) energy = 3VT (1/r + 1/R) is absorbed. (c) energy = 3VT (1/r - 1/R) is released (d) energy is neither released nor absorbed.

Answer: (c). Total volume V: area of small drops = 3V/r, area of big drop = 3V/R. Area decreases on merging, so energy is released. Energy released = 3VT(1/r - 1/R) So the answer is (c).

A certain number of spherical drops of a liquid of radius r coalesce… | NEET 2014 (AIPMT)

Q52NEET 2014 · AIPMTDifficult

Splitting & Merging of Drops

A certain number of spherical drops of a liquid of radius r coalesce to form a single drop of radius R and volume V. If T is the surface tension of the liquid, then

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Answer: (c)

Total volume $V$ : area of small drops $= \frac{3V}{r}$ , area of big drop $= \frac{3V}{R}$ .
Area decreases on merging, so energy is released.
Energy released $= 3VT\left(\frac{1}{r} - \frac{1}{R}\right)$
So the answer is (c).

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