Falling vertically in glycerine, a metal sphere has a mass of 50 mg...

The viscous force acting on a spherical body falling through a viscous medium is given by Stokes' law:

$F = 6 \pi \eta r v$

Given parameters are:
Coefficient of viscosity, $\eta = 8.0 \text{ poise} = 0.8 \text{ Pa s}$
Radius of the sphere, $r = 1 \text{ mm} = 10^{-3} \text{ m}$
Speed of the sphere, $v = 1 \text{ cm/s} = 10^{-2} \text{ m/s}$

Substituting the values into the formula:

$F = 6 \times 3.14 \times 0.8 \times 10^{-3} \times 10^{-2}$

$F = 15.07 \times 10^{-5} \text{ N}$

$F \approx 1.5 \times 10^{-4} \text{ N}$

The mass of the sphere and the density of glycerine are extraneous information for finding the viscous force at a specific speed.