1 7 By the parallelogram law, the total force F1 on the charge
q at A is given by
F1 = F 
1ˆr  where 
1ˆr  is a unit vector along BC The force of attraction or repulsion for each pair of charges has the
same magnitude F
q
=
2
0
2
4 π ε l
The total force F2 on charge q at B is thus F2 = F ˆr 2, where ˆr 2 is a
unit vector along AC