A simple pendulum has a length `l`, mass of bob `m`. The bob is given a charge `q`.The pendulum is suspended between the vertical plates of charged parallel plate capacitor. If `E` is the field strength between the plates ,then time period `T = `

Options

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

Answer

B

Explanation

Acceleration due ot electric field, `a=(qE)/(m)`.
As a is along g, so net acceleration `g.=g+a=g+(qE)/(m)`
`therefore T=2pisqrt((l)/(g+(qE)/(m)))`