Two particles, each with charge Q, and a third particle, with a charge q, are placed at the vertices of an equilateral triangle as shown.The total force on the particle with charge q is:

Question

Quizplus · Accepted Answer

Since the three particles are at the vertices of an equilateral triangle, the electric forces between the particles are symmetrical. Therefore, the force on the particle with charge q from the two particles with charge Q is directed along the line connecting the two vertices with charge Q, and it has the same magnitude. These two forces are equal in magnitude and opposite in direction, so they cancel each other out. The only force remaining is the force from the particle with charge q to the particle with charge Q, along the altitude of the equilateral triangle that passes through the particle with charge q. Therefore, the total force on the particle with charge q is perpendicular to the bottom side of the triangle.

Two Particles, Each with Charge Q, and a Third Particle