You mean like this? Not the most elegant, but serves as a good starting point for further fine tuning.
\documentclass[tikz,border=5pt]{standalone} \usetikzlibrary{patterns} \begin{document} \begin{tikzpicture}[>={stealth}] \draw [->] (-2.5,0) -- (2.5,0)node[below]{$x$}; \draw [->] (0,0)node[below, yshift=-0.1cm]{$O$} -- (0,2.5)node[left]{$y$}; \draw (2,0) arc (0:180:2); \draw [thick] (2,0.1) -- (2,-0.1)node[below]{$R$} (-2,.1) -- (-2,-0.1)node[below]{$-R$}; \draw [->] (0,0) -- node[above=.1cm]{$R$} ++(135:2) coordinate(d); \draw [dotted] (d) |- (0,0); \draw [pattern=north east lines] (1,0) rectangle (53:2)coordinate[pos=.5](c); \draw (c)+(-0.2,0)node[left]{$\hat{y}$} -- +(0.2,0)(c); \draw [|<-] (1,-.2) -- ++(-.3,0); \draw [|<-] (1.2,-.2) -- ++(.3,0); \node at (1.1,-.5) {$dx$} (20:1.6) node{$dA$}; \end{tikzpicture} \end{document}

simpleandthinwith reference to your question