Question

Two equal positive point charges 𝑞1 and 𝑞2 = 4.0 µC interact with point charge Q= 5.0 µC. Find the magnitude and direction of the net force on Q.

Answer 1

$$F_{net} = 2 | F | \cos \alpha$$

$$F=k\frac{qQ}{r^2}$$

$$\cos\alpha=\frac{4}{5}$$

$$F_{net}=2*9*10^9*\frac{4.0*10^{-6}*5.0*10^{-6}}{0.5^2}*\frac{4}{5}$$

$$F_{net}=\rm 1.15\: N$$

Force is directed in the +x direction.