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Physics - Fluid Question with Solution | TestHub

PhysicsFluidViscosityMedium2 minQB

PhysicsMediumsingle choice

A ball of radius R falls through oil with terminal velocity 5 cm/sec. Another ball of same material, has radius 3R. Its terminal velocity in the same oil will be [Use Stoke's law but neglect buoyant force]

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Answer:

Solution:

$v_{t, 1} = 5 cm/s$

$r_{1} = R$

$r_{2} = 3 R$

$6 π ηr v_{t} = \frac{4}{3} π r^{3} ρ g (buoyancy neglected)$

$v_{t} = \frac{2 ρ g r ^{2}}{9 η} \Rightarrow v_{t} \propto r^{2}$

$\frac{v _{t, 2}}{v _{t, 1}} = (\frac{3 R}{R})^{2} = 9$

$v_{t, 2} = 9 (5) = 45 cm/s$

$v_{t, 2} = 0.45 m/s (B)$

Stream:JEESubject:PhysicsTopic:FluidSubtopic:Viscosity

⏱ 2mℹ️ Source: QB

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