If the terminal speed of a sphere of gold (density: 19.5 kg/m3) is 0.2 m/s in viscous liquid (density : 1.5 kg/m3), find the terminal speed of a sphere of silver (density : 10.5 kg/m3) of the same size in the same liquid.

Terminal speed of spherical body in a viscous liquid is given byvT = 2r2(ρ-σ)g9ηwhere ρ = density of substance of body and σ = density of liquid.From given datavT(Ag)vT(Gold) = ρAg-σ1ρGold-σ1⇒vT(Ag) = 10.5-1.519.5-1.5×0.2 = 918×0.2 = 0.1 m/s