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What will be the approximate terminal ve...

What will be the approximate terminal velocity of a rain drop of diameter `1.8xx10^-3 m`, when density of rain water `~~10^3 kg. m^-3` and the coefficient of viscosity of air `~~1.8xx10^-5 N.s. m^-2` ?(Neglect buoyancy of air)

A

`49 m. s^-1`

B

`98 m . S^-1`

C

`392 m . S^-1`.

D

`980 m . S^-1`.

Text Solution

Verified by Experts

The correct Answer is:
B
`F=6pi eta r v[ v ` is the terminal velocity]
or, `mg=6pi eta r v or, 4/3 pi r^3 xx rho xx g = 6pi eta r v`
or, `v=(4pir^3 rho g)/(3xx6 pi eta r)=(2r^2 rho g)/(9eta0`
`=(2xx1.8xx1.8xx10^-6xx10^3xx9.8)/(4xx9xx1.8xx10^-5)=98m//s`
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