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

An isosceles triangle lying on its side. The two charges at the corners of the base of the isosceles triangle are labeled +5 C and +10 C. The top of the triangle is labeled +4 C with 4 vectors from it. The one east is labeled Y, the one west is labeled W, the one northeast is labeled X and the one southeast is labeled Z.
Which vector best represents the net force acting on the +4 C charge in the diagram?

W
X
Y
Z

1 answer

To determine which vector best represents the net force acting on the +4 C charge at the top of the isosceles triangle, we can analyze the forces exerted by the two other positive charges, +5 C and +10 C.

  1. Charge +5 C at the left base corner: This charge will exert a repulsive force on the +4 C charge. The force will be directed to the right and slightly downward (toward the base).

  2. Charge +10 C at the right base corner: Similarly, this charge will also exert a repulsive force, directed to the left and slightly downward (toward the base).

Since both of the charges are positive, the forces on the +4 C charge from the other two charges will both point away from them.

  • The force due to +5 C will be directed toward the right (east) and slightly down.
  • The force due to +10 C will be directed toward the left (west) and slightly down.

To find the net force, we need to combine both forces:

  • The rightward force from +5 C and the leftward force from +10 C will partially cancel each other. However, since +10 C is stronger, it will exert a comparatively larger leftward force on the +4 C charge.
  • Both forces have a downward component resulting from their angles.

The resultant vector will point primarily downward and to the left because the leftward force will dominate due to the stronger charge.

Considering the options provided (W, X, Y, Z):

  • W points directly to the left.
  • X points downward and left (which would include both horizontal and vertical components).
  • Y points directly upward.
  • Z points downward and to the right.

Given the analysis, Vector X, which points downward and slightly to the left, best represents the net force acting on the +4 C charge.