Question: The unit of potential energy is: [PMT/NEET-1991]
a. $g\ (\text{cm}/\text{sec}^{2})$
b. $g\ (\text{cm}/\text{sec})$
c. $g(\text{cm}^{2}/\text{sec}^{2})$
d. $g(\text{cm}/\text{sec})^{2}$

Answer: c. $g(\text{cm}^{2}/\text{sec}^{2})$

Solution: In CGS gravitation system,

potential energy $U=mgh$.

Unit: gram for mass, cm for length, sec for time, so

$[U]=g\cdot \text{cm}^{2}\cdot \text{sec}^{-2}$

i.e., erg.