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Physics - Fluid Question with Solution | TestHub

PhysicsFluidViscosityHard2 minPYQ_2010

PhysicsHardsingle choice

64 spherical rain drops of equal size are falling vertically through air with a terminal velocity $1.5 ms^{- 1}$ . If these drops coalesce to form a big spherical drop, then terminal velocity of big drop is

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Solution:

Volume of big drop $= 64 \times$ volume of a small drop $\Rightarrow \frac{4}{3} π R^{3} = 64 \times \frac{4}{3} π r^{3} \Rightarrow R = 4 r$ The terminal velocity of spherical rain drop $\Rightarrow ∴ v = \frac{2 r ^{2} ( ρ - σ )}{9 η} \Rightarrow v \propto r^{2} \frac{v _{1}}{v _{2}} = (\frac{r}{R})^{2} = (\frac{1}{4})^{2} = \frac{1}{16} v_{2} = 16 v_{1} = 16 \times 1.5 = 24 ms^{- 1}$

Stream:JIPMERSubject:PhysicsTopic:FluidSubtopic:Viscosity

⏱ 2mℹ️ Source: PYQ_2010

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