FBD Angle stopping

Question

This question is based off of the drawing in this link.

Code:

\documentclass[12pt]{article}
\usepackage{pgfplots}
\usepackage{tikz}
\usepackage{float}
\usetikzlibrary{calc, patterns, angles, intersections, quotes}
\usepackage[margin=1in]{geometry} 
\begin{document} 
    \begin{figure}[H]
        \begin{tikzpicture}[thick,>=latex]
            \begin{scope}
                \clip(-5,2) rectangle (5,-5);
                \pgfmathsetmacro{\leftPendPart}{-0.8/sqrt(2)}
                %\draw[dashed] (-4.24cm,0) arc(180:360:4.24cm);
                %\filldraw[white] (-4.3,4.3) rectangle (4.3,0);
                \draw[double distance=1.6mm] (0,0) -- (3,-3) node[midway,xshift=4mm,yshift=2mm]{$\ell$};
                \path[draw = none] (\leftPendPart mm, 0) -- ++ (-45:3) coordinate(pendTipLeft);
                \draw[->] (3,-3) -- (3,-4.5) node[below]{$mg$};
                \draw[fill=white] (-1.2,1.0) -- (-.5,0) arc(180:360:0.5) -- (1.2,1.0) -- cycle;
                \draw[draw=black,fill=white] (0, 0) circle circle (.3cm);
                \draw[draw=black,fill=white] (3,-3) circle circle (.3cm);
                \draw[dashed] (0, -0.5) coordinate (jointEdge) -- ++(270:3) coordinate(jointEdgeOut);
                \draw[->] (-0.7cm, 0) arc(180:360:0.7) node[pos = 0.4, xshift = -0.2cm, yshift = -0.2cm]{$bu$};
                \draw[->] (1.3, 0) arc(0:-45:1.3) node[pos = 0.2, xshift = 0.3cm, yshift = -0.2cm]{$c^*\dot{\theta}$};
                %\draw[->] (.6,0) -- (2,0) node[below]{$x$};
                %\draw[->] (0,-.6) -- (0,-2) node[below]{$y$};
                \draw[pattern=north east lines] (-1.4,1.3) rectangle (1.4,1);
                \pic[draw, ->, "$\theta$", angle eccentricity = 1.25, angle radius = 1.5cm]{angle=jointEdgeOut--jointEdge--pendTipLeft};   
            \end{scope}
        \end{tikzpicture}
    \end{figure}
\end{document}

Output:

I would like the arcs to stop right at the edge of the straight lines that has slope of -1. That is, the arcs coming from either side stop right at the line. Here's what I mean:

Desired (red arrows):

How to get something like that in the second pic (arcs don't have to be necessarily on the same location as the red arrows)?

Answer 1

A double line is just a thick line with a thinner (usually white) line on top. You may want to construct the double line as two separate lines, so that the angles can stop at them. This can be done with the shift right key and a couple of intersections.

\documentclass[12pt]{article}
\usepackage{tikz}
\usepackage{float}
\usetikzlibrary{arrows.meta,bending,calc, patterns, angles, intersections, quotes}
\usepackage[margin=1in]{geometry} 
\begin{document} 
    \begin{figure}[H]
        \begin{tikzpicture}[thick,>={Latex[bend]},
            bcirc/.style={circle,draw,inner sep=0pt,minimum size=0.6cm,fill=white},
            shift right/.style={to path={
             ($(\tikztostart)!#1!270:(\tikztotarget)$)
             --($(\tikztotarget)!#1!90:(\tikztostart)$) }}]
            \begin{scope}
                \clip(-5,2) rectangle (5,-5);
                \pgfmathsetmacro{\leftPendPart}{-0.8/sqrt(2)}
                %\draw[dashed] (-4.24cm,0) arc(180:360:4.24cm);
                %\filldraw[white] (-4.3,4.3) rectangle (4.3,0);
                \path[draw = none] (\leftPendPart mm, 0) -- ++ (-45:3) coordinate(pendTipLeft);
                \draw[->] (3,-3) -- (3,-4.5) node[below]{$mg$};
                \draw[fill=white,name path=arc] (-1.2,1.0) -- (-.5,0) 
                    arc(180:360:0.5) -- (1.2,1.0) -- cycle;
                \path (0,0) node[bcirc,name path=patha] (a){} 
                    (3,-3) node[bcirc,name path=pathb] (b){};
                \path[shift right=0.8mm,name path=ab1] (a) to (b);
                \path[shift right=-0.8mm,name path=ab2] (a) to (b);
                \draw[name intersections={of=pathb and ab1,by=i1},
                name intersections={of=pathb and ab2,by=i2},
                name intersections={of=patha and ab1,by=i1'},
                name intersections={of=patha and ab2,by=i2'},
                name intersections={of=arc and ab1,by=i3},
                name intersections={of=arc and ab2,by=i4}]
                 (i1) -- (i3) (i2) -- node[auto,swap] {$\ell$}(i4);
                \draw[dashed] (0, -0.5) coordinate (jointEdge) -- ++(270:3) 
                coordinate(jointEdgeOut);
                \draw[->] (-0.7cm, 0) arc(180:360:0.7) node[pos = 0.4, xshift = -0.2cm, yshift = -0.2cm]{$bu$};
                \draw[pattern=north east lines] (-1.4,1.3) rectangle (1.4,1);
                \path (i4) ++ (1,0) coordinate (aux);
                \pic[draw, <-, "$c^*\dot{\theta}$", angle eccentricity = 1.6, 
                    angle radius = 0.8cm,pic text options={yshift=2mm}]{angle=i2--i4--aux};   
                \path (intersection of jointEdgeOut--a and i1--i3) coordinate 
                 (aux2);
                \pic[draw, ->, "$\theta$", angle eccentricity = 1.25, 
                    angle radius = 1.5cm]{angle=jointEdgeOut--aux2--i1};   
            \end{scope}
        \end{tikzpicture}
    \end{figure}
\end{document}