Eight equal water drops are falling in air with a steady velocity `4cms^(-1)`​. If the drops coalesced what will be the new velocity :-

Options

A. `8cms^(-1)`
B. `2cms^(-1)`
C. `16cms^(-1)`
D. `32cms^(-1)`

Answer

C

Explanation

Terminal velocity `V=(2x^(2))/(9 eta) (rho-sigma)g`
`V prop r^(2) because ` volume conservation
`(V_(1))/(V_(2)) = ((r )/(R ))^(2) R =n^(1//3) r`
`R=(8)^(1//3) r =2r`
`(4)/( V_(2)) = ((r )/(2r))^(2) rArr V_(2) = 16 cm//s`