Question

what is the minimum magnitude of an electric field that balances the weight of a plastic sphere of mass 6.4 g that has been charged to -3.0 nc?

Answer 1

F = Q E force exerted by field on charge Q

F = M g weight of sphere

M g = Q E

E = M g / Q = .0064 kg * 9.80 m/s^2 / 3E-9 C

E = 2.09E7 Newtons/Coulomb