Edit and compile if you like:
\documentclass[tikz]{standalone}\begin{document}\begin{tikzpicture}[thick]% Axes\def\x{5}\def\y{3}\draw[->] (-\x-0.5,0) -- (\x+0.5,0) node[right] {$q_1$};\draw[->] (0,-\y-0.5) -- (0,\y+0.5) node[above] {$q_2$};% Ellipse\draw[blue,fill=blue,fill opacity=0.05] (0,0) circle [x radius=\x, y radius=\y];\coordinate[pin={[pin distance=25,scale=0.8]85:$\sqrt{2E/m}$}] (r1) at (\x,0);\coordinate[pin={[pin distance=25,scale=0.8]30:$\sqrt{2E/k}$}] (r2) at (0,\y);\node[blue] at (10:\x-1) {$P$};\end{tikzpicture}\end{document}
Click to download: shell.tex
Open in Overleaf: shell.tex
This file is available on tikz.netlify.app and on GitHub and is MIT licensed.
See more on the author page of Janosh Riebesell..