Data required: Exercise 2 : Comparing the k = 1/ (4peg) = 9.0 x 109 N m2 C-2 mass of an electron = 9.11 x 10-31 kg two forces mass of a proton = 1.67 x 10-27 kg G = 6.67 x 10-11 N m2 kg-2 . What is the force of repulsion between two electrons held one metre apart in a vacuum? What is the gravitational force of attraction between them? By what factor is the electric repulsion greater than the gravitational attraction