What is the minimum magnitude of an electric field that balances the weight of a plastic sphere of mass 14.2 g that has been charged to 7.7 nC. Give your answer to the nearest 0.1 MN/C (mega Newton per Coulomb)

18.1 MN/C

Explanation:

The gravitational force of the plastic sphere is in equilibrium with the electric force.

Mass of the plastic sphere = m = 14.2 g = 0.0142 kg

Force of gravity = F = mg = (0.0142) (9.81) = 0.139 N

This force is balanced by the electric force due to the charge 7.7 nC

Charge = q = 7.7 x 10⁻⁹ C

Electric field = E = F / q = (0.139) / (7.7 x 10⁻⁹) = 18.1 MN/C