15. it is a cloudy day and the clouds are charged. there is a downward electrostatic force of 3 x 10-6n acting on a -2 x 10-9 c charge that sits in the electric field. a) what is the magnitude of the electric field? b) what is the magnitude and direction of the electrostatic force on a proton placed in this field? c) what is the gravitational force on the proton?
