Question

A particle of mass $m$ and charge $q$ is projected vertically upwards. A uniform electric field $E$ is acted vertically downwards. The most appropriate graph between potential energy $U$ (gravitational plus electrostatic) and height $h$ ($<<$ radius of earth) is
(Assume $U$ to be zero on surface of earth.)

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

Potential energy at height $h$
$=-($Work done by gravity $+$ work done by electric field$)$
$=-(-mg-qE)h=(mg+qE)h$
The graph is a straight line passing though origin.