I want to redraw this image using TikZ:
I've written this code so far:
\documentclass[tikz]{standalone}
\usetikzlibrary{intersections}
\tikzset{help lines/.style={dashed, thick}}
\begin{document}
\begin{tikzpicture}[scale=3]
\clip (-2,-1.5) rectangle (1.5,1.5);
% draw x axis and small ticks at centers of circles
\draw[name path={xaxis}] (-2,0) -- (2,0);
\draw (-1.5,0.05) -- (-1.5,-0.05);
\draw (0,0.05) -- (0,-0.05);
% set coordinate of center of big circle
\coordinate (centerbig) at (-1.5,0);
% draw small circle and invisible big circle
\draw[name path={small circle}] (0,0) circle (1);
\draw[style=transparent,name path={big circle}] (-1.5,0) circle (2) {}; % just to get name for bigcircle
% calculate and name intersections of both circles and big circle with x axis
\draw [name intersections={of=small circle and big circle, by={first intersect, second intersect}}];
\draw[name intersections={of=big circle and xaxis, by={middle intersect}}];
% draw help lines of big circle
\draw[style=help lines] (middle intersect) arc (0:35:2);
\draw[style=help lines] (middle intersect) arc (0:-35:2);
% draw radius lines of big circle
\draw (centerbig) -- +(20:2);
\draw (centerbig) -- (second intersect);
% indicatior for diameter of small circle
\draw[thick,style = ->] (135:1.3) -- (135:1);
\draw[thick,style = ->] (-45:1.3) node[above right] {\(2 D\)} -- (-45:1);
% draw the section of big circle inside the small circle
\pgfsetlinewidth{1.5pt}
\pgfsetstrokecolor{black}
\pgfpathmoveto{\pgfpointanchor{first intersect}{south}}
\pgfpatharcto{2cm}{2cm}{1}{0}{0}{\pgfpointanchor{second intersect}{south}}
\pgfusepath{stroke}
\end{tikzpicture}
\end{document}
It yields this image:
As you can see, tthe indicator for the angle γ is missing.
To keep things tidy I am looking the an answer to another question:
How can I draw the arrows above the two lines reading vT and r?
(Answers to the other missing feature are also welcome...)
midway
option is equivalent to thepos=.5
option.