A steel ball of diameter 3 mm falls through glycerine and covers a distance of 25 cm in 10S. The specific gravity of steel and glycerine are 7.8 and 1.26 respectively. The viscosity of glycerine is about $pa^{-s}$
$ \eta = { 2 r^2 \over 9 } { (\rho - \sigma) g \over v_1 } $