Physics with Calculus II Question ?

Question

This is my first homework problem in this class and I don't understand it =.=;

"Two particles with equal mass have charges of 1.0 uC and 1.0nC, respectively. What must be their mass if their mutual gravitational attraction is to overcome their Coulomb repulsion?"

Answer 1

KQq/r^2 = F = GMm/r^2