Two parallel horizontal plates are 0.4 cm apart in air. An oil droplet of m = 4.9*10^-17 kg is introduced between the plates. If the drop has 2 electronic charges and if there is no air buoyancy, you can hold the droplet motionless between the plates if you keep the potential difference between them at...? Do I use delta V = -int[E*dl] from a to b? How would I incorporate the mass?