GATE MT 2018 Q46

The terminal velocity (𝑣) of a spherical inclusion of diameter D = 50 micrometers rising in liquid steel is_______ (in mm s^-1 to two decimal places).

Assume Stokes law; i.e., drag force 𝐹_𝑑 = 3𝜋𝜇𝐷𝑣, where 𝜇 is the viscosity of steel. Given: Density of liquid steel = 7900 kg m^-3; Viscosity of liquid steel = 0.0079 Pa s; Density of the inclusion = 2500 kg m^-3; Acceleration due to gravity = 9.8 m s^-2.