\documentclass[tikz]{standalone}\input{pre.tex}\begin{document}\begin{tikzpicture}
\draw[interface] (-2,0) rectangle ++ (4,0.5);
\draw[] (-2,0) -- ++(4,0);
\draw[line width=5pt, black!30] (0,0) -- (0,-1);
\draw[thick] (0,-1) circle (2pt) node[left, xshift=-0.5em] {$O$} -- ++ (-60:4);
\draw[axis,->] (0,-1) -- ++ (-60:5) node[below] {$+x$};
\draw[line width=5pt] (0,-1) ++ (-60:1.9) coordinate (1) ++ (-60:-0.1) -- ++ (-60:0.2);
\draw[axis] (0,-1) -- ++ (-90:4) node[below] {$$};
\draw[axis,->] (0,-1)++(-60:4) -- ++ (30:2) node[right] {$+\tau$};
\draw[force,->] (1) -- ++(120:1) node [right, xshift=0.25em] {$d\vec{T}$};
\draw[inforce,->] (1) -- ++(1,0) node [right] {$d\vec{F}_{in}$};
\draw[force,->] (1) -- ++(0,-1) node [below] {$dm\vec{g}$};
\contourlength{1mm};
\draw (2,-1) node[magenta] {$\bigotimes$} node[right, xshift=.5em, magenta] {$\vec{M}_{g}$};
\draw (3.5,-1) node[magenta] {$\bigodot$} node[right, xshift=.5em, magenta] {$\vec{M}_{in}$};
\draw[force,->,magenta] (0,-5) --++(0,1) node[above] {\contour{white}{$\vec{\omega}$}};
\draw[force,->,magenta] (-0.5,-5) --++(0,1) node[above] {\contour{white}{$\vec{N}$}};
\coordinate (ooo) at (0,-2);
\draw[line width=5pt] (0,-1) coordinate (o) ++ (-60:1.9) coordinate (oo) ++ (-60:-0.1) -- ++ (-60:0.2);
\draw pic["$\alpha$",draw=magenta,<-,angle eccentricity=1.2,angle radius=1.5cm] {angle=ooo--o--oo};
\end{tikzpicture}\end{document}
