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

\input{figsDefs.tex}

\begin{document}
	
\begin{tikzpicture}
	% trajectoire f=-0.25*(x)*(x-6)=-.25(x^2-6x)
	% derivée fp=-.5x+1.5
	\shorthandoff{:}
	\draw[-,blue,thick]
	plot[id=temp,smooth,domain=0:5,samples=30]function{-0.25*(x)*(x-6)};
	\draw[,fill] (5,1.25) circle (0.05);
	\shorthandon{:}
	\draw[-,,thick] (0,0) node[below] {instant $t_1$};
	\draw[,fill] (0,0) circle (0.05);
	\draw[-,blue,thick] (1,2) node[below] {$\Gamma$};
	\pgfmathsetmacro{\valX}{5};
	\pgfmathsetmacro{\valY}{-0.25*(\valX)*(\valX-6)};
	\path (\valX,\valY) node[below] {instant $t_2$};
	
	% vitesses
	\pgfmathsetmacro{\valX}{0};
	\pgfmathsetmacro{\valY}{-0.25*(\valX)*(\valX-6)};
	\pgfmathsetmacro{\valPente}{-.5*\valX+1.5};
	\pgfmathsetmacro{\valX}{4};
	\pgfmathsetmacro{\valY}{-0.25*(\valX)*(\valX-6)};
	\draw[fill] (\valX,\valY) circle (0.05) node[above=3pt] (P2) {CM};
	
	
	
	\pgfmathsetmacro{\valPente}{-.5*\valX+1.5};
	\path (1,\valPente) node[coordinate] (d) {};
	\path (\valPente,-1) node[coordinate] (n) {};
	\draw[->,thick,forceCol] (\valX,\valY) -- +(-2,-1) node[above,pos=0.7]
	{$\textcolor{red}{\vec{F}^\text{ext}}$};%
	\path (0,-2) node[coordinate] (A) {};
	\shorthandoff{!}
	\path ($(0,0)!(A)!(d)$) node[coordinate] (aT) {};
	\path ($(0,0)!(A)!(n)$) node[coordinate] (aN) {};
	\shorthandon{!}
	\draw[->,thick,deplCol] (\valX,\valY) -- +(aT) node[above right,pos=0.6]{$d\vec{r}_\text{CM}$};%
\end{tikzpicture}

\end{document}