Three charges are located at the vertices of a triangle, as shown.

3 charges are at the corners of an equilateral triangle with sides 1 m in length. The bottom two charges are each negative 4 Coulombs. The top charge is negative 3 Coulombs. There are vectors from the top charge north labeled W, south labeled Y, east labeled X, and west labeled Z.
Which vector best represents the net force acting on the –3 C charge in the diagram?

W
X
Y
Z

1 answer

To determine the net force acting on the -3 C charge located at the top vertex of the equilateral triangle, we need to consider the forces exerted by the other two -4 C charges located at the bottom vertices.

  1. Understanding the Configuration and Forces:

    • The charge at the top of the triangle (-3 C) will experience a repulsive force from both -4 C charges at the bottom. Since similar charges repel each other, the forces will act away from the two -4 C charges.
    • Let's denote the force exerted by the left -4 C charge (lower left corner) as \( F_{L} \) and the force exerted by the right -4 C charge (lower right corner) as \( F_{R} \).
  2. Calculating the Direction of Each Force:

    • The charge on the left (-4 C) will exert a force directed to the left (towards the left charge) at an angle toward the vertical due to the position of the charges.
    • The charge on the right (-4 C) will exert a force directed to the right (towards the right charge) at an angle toward the vertical.
  3. Force Vectors:

    • Let's analyze the forces in terms of their components:
      • The force from the left charge has components:
        • A horizontal component to the left.
        • A vertical component downward.
      • The force from the right charge has components:
        • A horizontal component to the right.
        • A vertical component downward.
  4. Net Force Calculation:

    • The vertical components from both left and right -4 C charges add together, creating a total downward force.
    • The horizontal components from both charges will cancel each other out, as one pushes left and the other pushes right.
  5. Conclusion:

    • The net force acting on the top -3 C charge will be directed straight down (towards the -4 C charges below).
    • In the context of the vectors labeled in the diagram, this direction corresponds with the vector labeled Y.

Thus, the vector that best represents the net force acting on the -3 C charge in the diagram is Y.