A simple pendulum consists of a small sphere of mass m suspended by a thread of length l. The sphere carries a positive charge q. The pendulum is placed in a uniform electric field of strength E directed vertically upwards. If the electrostatic force acting on the sphere is less than gravitational force then the period of pendulum is

Options

A. `T=2pi[(l)/(g-(qE)/(m))]^((1)/(2))`
B. `T=2pi[(l)/(g)]^((1)/(2))`
C. `T=2pi[(l)/(g+(qE)/(m))]^((1)/(2))`
D. `T=2pi[(ml)/(qE)]^((1)/(2))`

Answer

A

Explanation

Net acceleration `g.=g-(qE)/(m)`
So, `T=2pisqrt((l)/(g.)), T=2pisqrt((l)/((g-gE//m)))`