\documentclass[convert=true,convert={convertexe={convert},density=1200,outext=.png}]{standalone}

\input{figsDefs.tex}

\begin{document}
	
\begin{tikzpicture}%
	% cercle osculateur
	\pgfmathsetmacro{\myRad}{sqrt(5)};
	%\draw[-,dashed] (0,0) circle (\myRad);
	% trajectoire f=1./48.*(-2*x*x*x-9*x*x+107)
	\shorthandoff{:}
	\draw[-,thick,scale=0.98] plot[id=temp,smooth,domain=-2.5:3,samples=30] function{1./48.*(-2*x*x*x-9*x*x+107)} node[left=3pt] {support};
	\draw[-,thick,blue] plot[id=temp,smooth,domain=1:3,samples=30] function{1./48.*(-2*x*x*x-9*x*x+107)};
	\pgfmathsetmacro{\aParab}{-0.15}
	\pgfmathsetmacro{\bParab}{-0.5-2*\aParab}
	\pgfmathsetmacro{\cParab}{2-\aParab-\bParab}
	\draw[-,thick,blue] plot[id=temp,smooth,domain=-2.5:1,samples=30] function{\aParab*x*x+\bParab*x+\cParab};
	\draw[blue] (-2.3,2.5)  node {$\Gamma$};
	\shorthandon{:}
	% point 1
	\path (1,2) node[coordinate] (A) {};
	\draw[blue,fill=blue] (A) circle (0.05);%
	\draw[blue] (A) node[above=3pt] {$D$};%
	\draw[forceCol] (A)+(.1,.2) node[right] {$\vec{S}=\vec{0}$};%
	%\draw[decorate,decoration={brace,raise=3pt}] (0,0) -- node[above=2mm,sloped] {$R$} (A);
	% point 2
	\path (2.5,0.40625) node (B) {};
	\draw[blue,fill=blue] (B) circle (0.05) node[below left] {$P$};%
	\shorthandoff{:}
	\draw[->,>=latex,thick,forceCol] plot[id=temp,domain=2.5:3.5,samples=2] function{32./55.*(x-2.5)+0.40625};
	\draw[forceCol] (3,1.3) node {$\vec{S}\neq\vec{0}$};
	\shorthandon{:}
	
	% vecteurs
	\draw[->,>=latex] (1,2) -- (1-.5,2-1) node[right=2pt,pos=0.8] {$\vec{e}_n$};%
	\draw[->,>=latex,thick,vitCol] (1,2) -- +($1.5*(-1,.5)$) node[above,pos=0.5] {$\vec{v}_D$};%
	
	% origine : centre du cercle
	%\draw[fill] (0,0) circle (0.05) node[below right,pos=1] {$C$};%
\end{tikzpicture}%

\end{document}