Force from multiple charges (electric forces) question

Question

Particles q1, q2, and q3 are in a straight line. Particles q1= -5.00x10^-6C, q2= -5.00x10^-6C, and q3= -5.00x10^-6C. Particles q1 and q2 are separated by 0.500m. Particles q2 and q3 are separated by 0.500m. What is net force on q3?

Answer 1

First, draw a diagram with charges left to right: q1 q2 q3 and draw the forces acting on q3 based on the direction of the force and the charges.

Don't worry about the signs of the charges in the equation. You take care of the force directions.

F_e,ij = k_e q_iq_j/d² 1st: All the charges are negative so both q1 and q2 push q3 to the right. Therefore, their forces on three will add:

F₁₃ + F₂₃ = k_e(5x10^-6 C)²/ (10 m)² + k_e(5x10^-6 C)²/ (5 m)²

Hope that helps!