Question

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

Answer 1

W.

Both bottom −4 C charges repel the −3 C charge. Those two forces are symmetric, pointing up-right and up-left, so their horizontal components cancel and their vertical components add — giving a net force straight up (north).