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..