In Millikan’s oil drop experiment, what is the terminal speed of an uncharged drop of radius 2.0 × 10–5 m and density `1.2 × 10^3` kg `m^(–3)`. Take the viscosity of air at the temperature of the experiment to be `1.8 × 10^(–5)` Pa s. How much is the viscous force on the drop at that speed ? Neglect buoyancy of the drop due to air.