The force on charge q1 due to charge q2 is
F1 = (1/4πεo) * (q1q2/r2)
or F1 = (9 * 109) * [(4 * 10-6 * 4 * 10-6)/(20 * 10-2)2]
or F1 = 3.8 N
The force on charge q1 due to charge q3 is
F2 = (1/4πεo) * (q1q3/r2)
or F2 = (9 * 109) * [(4 * 10-6 * -4 * 10-6)/(20 * 10-2)2]
or F2 = -3.8 N
The net force on the charge q1 is
Fnet = [F12 + F22 + 2F1F2cosθ]1/2
or F
net = [(3.8)
2 + (-3.8)
2 + 2 * 3.8 * -3.8 * cos(60
o)]
1/2
or Fnet = [14.44]1/2 = 3.8 N
The center of the triangle is at a distance of 8.66 cm from the vertices of the triangle.
The electric field at the center of the triangle is
E = (1/4πεo) * (2q/r2)
or E = 9 * 109 * [(2 * 4 * 10-6)/(20 * 10-2)2]
or E = 18 * 105 N/C = 1800 * 103 N/C
or E = 1800 kN/C