Question

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 magnitude of the resultant force on the charged particle at A is
(a) zero
(b) 3.6 N
(c) 3.6√3 N
(d) 7.2 N

Answer 1

(a) zero

Using, F_net = ma,
a = 0 ⇒ F_{net = 0}
As the whole system is at rest, the resultant force on the charged particle at A is zero.