Three rigid rods are joined to form an equilateral triangle ABC of side 1 m. Three particles carrying charges 20 μC each are attached to the vertices of the triangle. The whole system is at rest in an inertial frame. The resultant force on the charged particle at A has the magnitude
Since the net acceleration is = 0 for the system, the net force must also be zero.
∵ 
and 
thus 
1