Which vector best represents the net force acting on the -3 c charge in the diagram

w
x
y
z

 W is the correct answer.

Explanation:

   Since the charges are negative the forces acting is repulsive.

   The left -4C charge repulse -3C, the force is shown in figure given as F2

   The right -4C charge repulse -3C, the force is shown in figure given as F1

    Since the charge magnitudes are same the magnitude of F1 and F2 are same, but their direction is different. From second figure we can see the angle between forces and W is 30⁰.

  On resolving vectors the force along Z = F1 sin 30 and force along X = F2 sin 30

  Since magnitudes are same they cancel each other.

   Force along W = F1 cos 30 + F2 cos30 = 2Fcos 30 (Say F1 = F2 = F)

So net force is directed towards Z.