A small metal ball of diameter `4 mm` and density `10.5 g//cm^(3)` in dropped in glycerine of density `1.5 g//cm^(3)`. The ball attains a terminal velocity of `8cm s^(-1)`. The coefficient of viscosity of glycerine is

Options

A. 4.9 poise
B. 9.8 poise
C. 98 poise
D. 980 poise

Answer

B

Explanation

` V_T = (2 r ^ 2 ) /( 9 ) ((rho - rho ' ) /(eta )) g, eta = (2 r ^2 (rho - rho' ) g )/( 9 v_T) cong 9.8 ` poise