Object A of charge 5e-6 C is located at the origin of a coordinate plane. Object B of charge 3e-6 C is located on the x-axis of a coordinate plane at x = 0.002 m. Object C of charge 3e-6 C is located on the y-axis of a coordinate plane at y = 0.001 m. Calculate the direction (angle formed with the positive x-axis) of the net electrical force exerted on object A by objects B and C.

Question

The answer given is 255.964 degrees, but I dont understand how

Answer 1

compute the force in neg y direction due to C, compute the force in the neg x direction due to A.
So the resultant will be in the -x,-y direction.

Tan Theta=-yforce/-xforce
Now, that will give you the principle solution, add 180 deg to get to quadrant III.