1. The problem statement, all variables and given/known data The picture shows a small 2g mass suspended from a massless thread. When a horizontal electric field of 2000 N/C pointing left to right is applied, the mass moves to the position shown and then comes to a stop. Calculate the magnitude of the charge on the mass. http://imgur.com/3uSDc [Broken] 2. Relevant equations Coulomb's Law: F= (k*q1*q2)/r2 F=qE 3. The attempt at a solution I know the charge is negative by the picture, but I can't use these equations without more information. Am I missing an equation I should know or just a concept that lets me ignore something?