A small object of mass 3.00 g and charge -13 µC "floats" in a uniform electric field. What is the magnitude and direction of the electric field?

Answer 1

This may seem tricky but the key to realize is that electric forces and gravitational forces = 0. In this case Mg=Eq since the charge floats in the electric field. there the equation = E=mg/q and that'll be your answer. (You can solve the math).