Question

Three point charges of 3µC, 8µC and 5µC are located at the corners of an equilateral triangle of side 0.4m, calculate the net force on the 8µC?

Answer 1

The components of a net force on a second charge

$$F=\sqrt{F_{12}^2+F_{32}^2-2F_{12}F_{32}\cos 120^{\circ}}$$

$$=\frac{k q_2}{a^2}\sqrt{q_1^2+q_3^2+q_1q_3}$$

$$=\frac{9\times 10^9\times 8\times 10^{-6}}{(0.4)^2}\sqrt{3^2+5^2+3\times 5}\times 10^{-6}$$

$$=3.15\:\rm{N}$$