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Question:

The bob of a simple pendulum has mass 2g and a charge of 5.0µC. It is at rest in a uniform horizontal electric field of intensity 2000 V/m. At equilibrium, the angle that the pendulum makes with the vertical is : (take g=10 m/s²)

tan⁻¹(5.0)

tan⁻¹(2.0)

tan⁻¹(0.2)

tan⁻¹(0.5)

Solution:

Correct option is C. tan⁻¹(0.5)
tan θ = qE/mg = 5 × 10⁻⁶ × 2000 / 2 × 10⁻³ × 10
tan θ = 1/2 ⇒ θ = tan⁻¹(0.5).