Question

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

• A. ${\tan }^{-1}\left(5.0\right)$
• B. ${\tan }^{-1}\left(2.0\right)$
• C. ${\tan }^{-1}\left(0.5\right)$
• D. ${\tan }^{-1}\left(0.2\right)$

Answer 1

The correct option is C ${\tan }^{-1}\left(0.5\right)$

$\tan \theta =\frac{qE}{mg}=\frac{5\times {10}^{-6}\times 2000}{2\times {10}^{-3}\times 10}$
$\tan \theta =\frac{1}{2}\Rightarrow \theta ={\tan }^{-1}\left(0.5\right)$.