In Millikan’s oil drop experiment, what is the terminal speed of an uncharged drop of radius 2.0×10^−5 m and density 1.2×10^23 kgm^−3 . Take the viscosity of air at the temperature of the experiment to be 1.8×10^−5 Pas. How much is the viscous force on the drop at that speed ? Neglect buoyancy of the drop due to air.