I assume that that you are typesetting in-line maths rather than display maths. In which case the use of \sqrt
introduces some extra interline spacing. In this case it is better to use \surd
(which only sets the root sign with no horizontal bar) instead of \sqrt
.
\documentclass{article}
\begin{document}
Just a bit of text to set the scene, hopefully longer than a line but
if not it probably doesn't matter
Some maths $\sqrt{2}$ and $\surd{2}$ and $\sqrt{GM/a_p^3}$ and
$\surd{(GM/a_p^3)}$ end in-line maths. But perhaps a little more text
is required to provide a line after the maths to provide some after
context.
\end{document}
My apologies, whenever I try to post a result it never works. Please compile the above yourself.

EDIT
With thanks to whoever posted the result above.
If you are going to use a surd instead of a square root then it is useful to have an extensible version.
\newcommand*{\absurd}{\delimiter"270370 }
\newcommand*{\Surd}[1]{\left\absurd{#1}\right.\kern-\nulldelimiterspace}
where \Surd
is a vertically expansible version of \surd
It can be used like this:
\[
\surd{(GM/a_p^3)} \Surd{\left(\frac{GM/a_p^3}{GM/a_p^3}\right)}
\]