A pendulum bob of mass `30.7 xx 10^(-6)kg` and carrying a chargee `2 xx 10^(-8)C` is at rest in a horizontal uniform electric field of `20000V//m`. The tension in the thread of the pendulum is `(g = 9.8 m//s^(2))`

Options

A. `3 xx10^(-4) N`
B. `4 xx10^(-4) N`
C. `5 xx10^(-4) N`
D. `6 xx10^(-4) N`

Answer

C

Explanation

`T=sqrt((mg)^2+(qE)^2)`
`=sqrt((30.7xx10^(-6)xx9.8)^(2)+(2xx10^(-8)xx2 xx10^4)^2)`
`=sqrt(2.50 xx10^(-7))`
`~~5 xx10^(-4) N`