Four point charges are at the corners of a square of side a as shown in the figure below. Determine the magnitude and direction of the resultant electric force on q, with ke, q, and a left in symbolic form. (B = 4q and C = 6.5q. Let the +x-axis be pointing to the right.)

Question

b|---a----|q
| |
a a
| |
c|_ _ _ a _ _|b

Answer 1

Easy. the adjacent charges both b have forces at 90 degrees, so they add equally diagonally F=2k(4q^2)/a^2 * sin45

then add to that the diagonal force
Fd= k6.5q^2/(asqrt2)^2

now add those two forces. Your teacher is top easy.