Answer:
F = -51.357i -29.958j
abs(F) = 59.45 N
Step-by-step explanation:
To solve the problem we use coulomb's law with vectorial notation, F = q1*q2/(4*pi*eo*r^2) where q1 and q2 are the charges and r is the distance between them:
Point B exerts a force on A in '-i' direction
Point C exerts a force on A in '-j' direction
Fba = 4*7/(4*pi*eo*0.07^2) = 51.357N
Fca = 4*3/(4*pi*eo*0.06^2) = 29.958N
F = -51.357i -29.958j
abd(F) = 59.45 N