In Millikan’s oil drop experiment, what is the terminal speed of an uncharged drop of radius \(2\times10^{-5}\) m and density \(1.2\times10^{3}\) kg-m^–3?
(Take the viscosity of air at the temperature of the experiment to be \(1.8\times10^{-5}\) Pa-s.)
1. \(2.7\) cm/s
2. \(3.9\) cm/s
3. \(5.8\) cm/s
4. \(4.6\) cm/s