\documentclass[tikz]{standalone}\input{pre.tex}\begin{document}\begin{tikzpicture}
\fill[magenta!10, draw=none] (0,0) rectangle ++(2,3);
\fill[magenta!10, draw=none] (0.8,0) rectangle ++(0.4,-0.5);
\draw (0,3.2)--(0,0)--(2,0)--(2,3.2);
\draw[magenta!10] (0.8,0) -- ++(0.4,0);
\draw[magenta] (1,0.3) circle (2pt) node[above, yshift=0.5em] {$A$};
\draw[magenta] (1,-0.3) circle (2pt) node[below, yshift=-0.5em] {$B$};
\draw[magenta,->] (1.4,0.3) -- ++(0,-0.5) node[below] {$\vec{v}$};
\draw[magenta,->] (0.6,-0.3) -- ++(0,-1) node[below] {$\vec{v}_2$};
% Draw line annotation
% Input:
% #1 Line offset (optional)
% #2 Line angle
% #3 Line length
% #5 Line label
% Example:
\lineann[0.5]{90}{3}{$h(t)$}
\draw[axis,->] (-1,-0.5) -- ++(0,4) node[above] {$+h$};
\end{tikzpicture}\end{document}
