Chapter 21, Problem 10Q

In Fig. 21-19, a central particle of charge −2q is surrounded by a square array of charged particles, separated by either distance d or d/2 along the perimeter of the square. What are the magnitude and direction of the net electrostatic force on the central particle due to the other particles? (Hint: Consideration of symmetry can greatly reduce the amount of work required here)

Figure 21-19 Question 10.