A charged oil drop of density $$880\ \text{kg m}^{-3}$$ is held stationary between two parallel horizontal metal plates 6.0 mm apart when a potential difference of $$V = 103$$ volt is applied between the two plates. When the electric field is switched off, the drop falls. At a certain time the drop is seen to fall a distance of 2.0 mm in 35.7 s and next 1.2 mm in 21.4 s. The upper plate in the experiment is at higher potential. Given that the viscosity of air is $$1.80\times 10^{-5}\ \text{Nsm}^{-2}$$ and density of air is $$1.29\ \text{kg m}^{-3}$$