four equal point charges +3.0 x 10^-6 C are placed at the four corners of a square that's 40cm on a side . find the force on any one of the charges.

Answer 1

due to symettry, you only have to consider the component along the diagonal. Think that out.

force=kq^2 (.707/.4^2 + .707/.4^2 + 1/(.4*1.414)^2 )