\documentclass[tikz]{standalone}\input{pre.tex}\begin{document}\begin{tikzpicture}
% \begin{scope}[opacity=0.4]
% \node[cargo] (I) at (2,0) {} node[above of=I, yshift=-1.3em] {};
% \draw[draw=black!80,decoration={aspect=0.3, segment length=1mm, amplitude=2mm,coil},decorate] (0,0) -- node[above, black, pos=0.5, yshift=1em] {} (I);
% \draw[] (4,-1.1) -- ++(0,0.2) node[below, yshift=-5pt, black] {$l$};
% \end{scope}
\draw[interface,fill=white!40, draw=black] (0,0.1) rectangle ++(5,-0.2);
\draw[interface,fill=magenta!30, draw=black] (3,0.1) rectangle ++(0.5,-0.2);
% \node[cargo] (b) at (4,0) {} node[above of=b, yshift=-1.3em] {$m$};
% \draw[draw=black!80,decoration={aspect=0.3, segment length=1.5mm, amplitude=2mm,coil},decorate] (0,0) -- node[above, black, pos=0.5, yshift=1em] {$k$} (b);
\draw[] (0,-1.1) -- ++(0,0.2) node[below, yshift=-5pt, black] {$0$};
\draw[] (3,-1.1) -- ++(0,0.2) node[below, yshift=-5pt, black] {$x$};
\draw[] (3.5,-1.1) -- ++(0,0.2) node[below, yshift=-5pt, black] {\tiny$x+dx$};
\draw[] (5,-1.1) -- ++(0,0.2) node[below, yshift=-5pt, black] {$\frac{l}2$};
\draw[axis,->] (0,-1) -- ++(6,0) node[right, black] {$x$};
\draw[fill=black] (0,0) circle (0.1);
% \draw[force,->] (3,0) -- ++(-0.5,0) node[above, yshift=0.5em, black] {$\vec{f}_e$};
\draw[force,->] (3.5,0) -- ++(0.5,0) node[above, yshift=0.5em, xshift=1em, black] {$\vec{F}(x+dx)$};
\draw[force,->] (3,0) -- ++(-0.5,0) node[above, yshift=0.5em, xshift=-1em, black] {$\vec{F}(x)$};
\node[left] at (-0.4,-0.4) {$\bigotimes\vec\omega$};
\end{tikzpicture}\end{document}
