A simple pendulum has a bob with mass m and charge q. The pendulum string has negligible mass. When a uniform and horizontal electric field E is applied, the tension in the string changes. The final tension in the string, when pendulum attains an equilibrium position i $s _____.$
(g : acceleration due to gravity)

Question

A simple pendulum has a bob with mass m and charge q. The pendulum string has negligible mass. When a uniform and horizontal electric field E is applied, the tension in the string changes. The final tension in the string, when pendulum attains an equilibrium position i $s _____.$

(g : acceleration due to gravity)

G1 Physics · Accepted Answer

At equilibrium, three forces act on the bob: 1. Weight mg vertically downward. 2. Electric force qE horizontally. 3. Tension T along the string. For equilibrium, the tension balances the vector resultant of the weight and electric force. Since mg and qE are mutually perpendicular, T² = (mg)² + (qE)². Therefore, T = √(m²g² + q²E²). Correct option: C.