We are given the following information.
Charge: q1 = q2 = q3 = 22.0x10-6 C
Equilateral triangle of side = 0.111 m
We are asked to find the magnitude of the net force on the top charge (q1).
The force on charge q1 due to the charge q2 is given by

Where k is the coulomb's constant (k = 9×10⁹).

The force on charge q1 due to the charge q3 is given by

The angle between force F1 and F2 is 60°.
The resultant force on charge q1 is given by

Therefore, the magnitude of the net force on the top charge is 612.35 N.