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Physics - Fluid Question with Solution | TestHub

PhysicsFluidSurface TensionHard2 minPYQ_2014

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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:NEET 2014

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Answer:

Solution:

$∆ U = (S T) (∆ A)$
$A (i n i t i a l) = (4 π r^{2}) n$
$A (f i n a l) = 4 π R^{2}$
$∆ A = (4 π r^{2}) n - 4 π R^{2}$
$(\frac{4}{3} π r^{3}) n = \frac{4}{3} π R^{3}$
$n = \frac{R^{3}}{r^{3}}$
$∆ A = 4 π [\frac{R^{3}}{r^{3}} . r^{2} - R^{2}] = 4 π [\frac{R^{3}}{r} - \frac{R^{3}}{R}] = (\frac{4 π R^{3}}{3}) 3 [\frac{1}{r} - \frac{1}{R}]$
$∆ A = 3 V [\frac{1}{r} - \frac{1}{R}]$
$∆ U = 3 V T [\frac{1}{r} - \frac{1}{R}]$

Stream:NEETSubject:PhysicsTopic:FluidSubtopic:Surface Tension

⏱ 2mℹ️ Source: PYQ_2014

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