Three charges are arranged as follows: +3 mC located on the y-axis at +15 mm; -2.5 mC located on the x-axis at -25 mm; and +4.0 mC located at the origin. Determine the magnitude of the force acting on the charge located at the origin.

Answer 1

Use coulombs law, add the forces as vectors. You have a S force from the y charge, and a W force from the x axis charge.