Question

A particle of mass $m$ and charge $q$ is attached to a light rod of length $L$. The rod can rotate freely in the plane of paper about the other end, which is hinged at $P$. The entire assembly lies in a uniform electric field $E$ also acting in the plane of paper as shown. The rod is released from rest when it makes an angle $\theta$ with the electric field direction. Determine the speed of the particle when the rod is parallel to the electric field.

Answer 1

Mass$=m$

Charge$=q$

Length$=l$

$qV=\frac{1}{2}{v}_{speed}^2\frac{2qV}{m}=v_{speed}^2{v}_{speed}=\sqrt{\frac{2qV}{m}}$