Question

There are four charges, each with a magnitude of 2.20

Answer 1

For this to occur the like charges must be opposite each other.

The Force due to the opposite charge will be away from the center

and = k*q^2/r^2 = 9.0x10^9*(2.2x10^-6)^2/(0.39*sqrt(2))^2 = 0.143N

It components along the sides are 0.143*cos(45) and 0.143*sin(45) = 0.101N

Now the charges adjacent create force = k*q^2/r^2 = 9.0x10^9*(2.2x10^-6)^2/0.39^2 = 0.286N

Now adding we get Fx = 0.286 - 0.101 = 0..185N and Fy = 0.286-0.101 = 0.185N

So F = sqrt(Fx^2 + Fy^2) = sqrt(0.185^2 + 0.185^2) = 0.2616N