posted by ALICIA .
An oil drop is stationary within an electric field of 490 V/m that is set up between two parallel plates. If the volume of the oil drop is 4 X 10 (-19) m3, how many excess electrons does it carry?
(I'll give ya'll just one hint: the fundamental unit of charge e = 1.6 X 10 (-19) C. )
downward force= mg
upward force= Eq
so what is the mass? density*volume
so you need the density of the oil
number electrons= q/e