A raindrop with radius $R=0.2\, {mm}$ fells from a cloud at a height $h=2000\, {m}$ above the ground. Assume that the drop is spherical throughout its fall and the force of buoyance may be neglected, then the terminal speed attainde by the raindrop is : (In ${ms}^{-1}$)
[Density of water $f_{{w}}=1000\;{kg} {m}^{-3}$ and density of air $f_{{a}}=1.2\; {kg} {m}^{-3}, {g}=10 \;{m} / {s}^{2}$ Coefficient of viscosity of air $=18 \times 10^{-5} \;{Nsm}^{-2}$ ]
$14.4$
$2.47$
$43.56$
$4.94$
A lead shot of $1mm$ diameter falls through a long column of glycerine. The variation of its velocity $v$. with distance covered is represented by
The average mass of rain drops is $3.0\times10^{-5}\, kg$ and their avarage terminal velocity is $9\, m/s$. Calculate the energy transferred by rain to each square metre of the surface at a place which receives $100\, cm$ of rain in a year
Velocity of water in a river is
Write one of the practical use of viscosity.
In Millikan's oll drop experiment, what is the terminal speed of an uncharged drop of radius $2.0 \times 10^{-5} \;m$ and density $1.2 \times 10^{3} \;kg m ^{-3} .$ Take the viscosity of air at the temperature of the experiment to be $1.8 \times 10^{-5}\; Pa\; s$. How much is the viscous force on the drop at that speed? Neglect buoyancy of the drop due to atr.