A typical raindrop is about 4 mm in the diameter. If a raindrop falls from a cloud which is at 1 km above the ground, estimate its momentum when it hits the ground.

Explanation

Diameter , D=4m
`implies ` radius, r=2mm = `2 times 10^-3`m
mass of rain drop = volume `times` density
`=4/3pir^3times1000m`
(`because` mass of one `m^3` of water =1000 kg)
`thereforem=4/3times22/7times[2times10^-3]^3times1000`
=`33.52 times 10^-6kg`
Velocity of rain drop `v=sqrt(2gh)`
But h= 1km =1000 m
`thereforev=sqrt(2times9.8times1000)=sqrt19600`
`=140m//sec`.
Momemtum of rain drop , `vec(p)=mv`
`=33.5times10^-6times140`
`=4.693times10^-3kg-m`