# Three equal charges (Q, each) are placed on the vertices of an equilateral triangle of side a. What is the resultant force on any one charge due to the other two?

The charges are shown in figure. The resultant force
$F=\sqrt {F_1^2 +F_2^2+2F_1F_2 \cos 60}$
with $F_1=F_2=\large\frac{kQ^2}{a^2}$
$f= \large\frac{\sqrt 3 kQ^2}{a^2}$
From symmetry the direction is as shown along y-axis.