JEE PHYSICS MCQ: MECHANICAL PROPERTIES OF FLUIDS

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Application +4 | -1

In Millikan's oil drop experiment, what is the terminal speed of a drop of radius

2.0 \times 10^{-5} \mathrm{~m}

and density

1.2 \times 10^3 \mathrm{~kg} \mathrm{~m}^{-3}

? Take the viscosity of air at the temperature of the experiment to be

1.8 \times 10^{-5} \mathrm{~Nsm}^{-2}

. How much is the viscous force on the drop at that speed? Neglect buoyancy of the drop due to air.

View answer and explanation

Correct option: A

3.9 \times 10^{-10} \mathrm{~N}

Option A (

3.9 \times 10^{-10} \text{ N}

) is correct because it is calculated using Stokes' law for viscous force at terminal speed.

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80 \mathrm{~kg}

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