Ecco altre due immagini che ho realizzato alla buona. Se avete suggerimenti su come migliorarne il (pessimo) codice, sono qui. Ah, per tutta una serie di ragioni (molte delle quali certamente infondate) sono fermo alla MacTeX 2013, quindi vi chiedo di evitare librerie troppo moderne.
`\documentclass{article}
\usepackage[dvipsnames]{xcolor}
\usepackage{tikz,pgfplots,amsmath}
\begin{document}
\begin{tikzpicture}[font=\small]
\begin{axis} [width=0.4\textwidth,
axis lines=middle,
xmin=0,xmax=4,ymin=0,ymax=20,
enlargelimits,
grid,
xtick={1,2,3,4,5,6},
ytick={5,10,15,20},
xlabel=$x$,
ylabel=$y$]
\addplot [domain=0:10, samples=100,smooth,blue,very thick] {5/x};
\end{axis}
\end{tikzpicture}
\begin{tikzpicture} [decoration={coil,aspect=0.3,segment length=1mm,amplitude=1mm},font=\small,scale=1.15]
\draw [thick] (0,0) — (4.5,0) — (0,2.59808) — cycle;
\draw [thick,fill=BrickRed!50!white,rounded corners,shift={(2.10192,1.84641)},rotate =-30] (-0.9,-0.4) rectangle (0.9,0.4);
% asse x
\draw [->,shift={(2.10192,1.84641)},rotate =-30] (0,0) — (1.5,0);
\node [shift={(2.10192,1.84641)},rotate =-30,below=5pt] at (1.75,0) {$x$};
% asse y
\draw [->,shift={(2.10192,1.84641)},rotate =-30] (0,0) — (0,1.75);
\node [shift={(2.10192,1.84641)},rotate =-30,right=20pt] at (0,2) {$y$};
\draw [->,shift={(2.10192,1.84641)},rotate =-30] (0,0) — (1.5,0);
% P
\draw [blue,very thick,->] (2.10192,1.84641) — (2.10192,0.34641);
\node
at (2.10192,0.34641) {$\vec{P}$};
% P perpendicolare
\draw [blue,very thick,->,shift={(2.10192,1.84641)},rotate =-30] (0,0) — (0,-1.29904);
\node [below] at (1.3,0.9) {$\vec{P}_{\bot}$};
% P parallelo
\draw [blue,very thick,->,shift={(2.10192,1.84641)},rotate =-30] (0,0) — (0.75,0);
\node [below] at (2.7,2.1) {$\vec{P}_{\parallel}$};
% reazione vincolare
\draw [blue,very thick,red,->,shift={(2.10192,1.84641)},rotate =-30] (0,0) — (0,1.29904);
\node
at (2.7,2.6) {$\vec{F}_{\text{v}}$};
% forza elastica
\draw [blue,very thick,green,->,shift={(2.10192,1.84641)},rotate =-30] (0,0) — (-0.75,0);
\node [below] at (1.7,2.7) {$\vec{F}_\text{e}$};
\draw [<->,dashed] (-0.25,-0) — (-0.25,2.59808);
\node
at (-0.25,1.29904) {$h$};
\draw [<->,dashed] (0,-0.25) — (4.5,-0.25);
\node [below] at (2.25,-0.25) {$d$};
\draw
(-2.75,-0.1) rectangle (-2,0.1);
\draw [dashed,shift={(2.10192,1.84641)},rotate =-30] (0,-1.3) — (0.75,-1.3);
\draw [dashed,shift={(2.10192,1.84641)},rotate =-30] (0.75,-1.25) — (0.75,0);
\draw [decorate,shift={(2.10192,1.84641)},rotate =-30] (-2.0,0.0) — (-0.9,0.0);
\end{tikzpicture}
\end{document}`