A gas bubble of 2 cm diameter rises through a liquid `1.75 gm cm^(-3)` with a fixed speed of `0.35 cm s^(-1)`.Naglect the density of the gas. The cofficient of viscosity of the liquid is

Options

A. 870 poise
B. 1120 poise
C. 982 poise
D. 1089 poise

Answer

D

Explanation

As gas bubble is moving upward with constant speed so, buoyant force = viscous drag force

`rArr F_b = F_v`
` rArr (4/3 pi r^3) rho g = 6pi eta rv`
` rArr eta = 2/9 (r^2 rho g)/(v )`
Here `r = 1cm, rho = 1.75 g cm^(-3) , g = 980 cms^(-2)`
`v = 0.35 cms^(-1), eta = ? `
` therefore eta = 2/9 xx (t^2 xx 1.75 xx 980)/(0.35) = 1088.88 = 1089` poise