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Sistema vibratorio en LaTeX con TikZ: desplazando el péndulo existente a un punto concreto

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Sistema vibratorio en LaTeX con TikZ: desplazando el péndulo existente a un punto concreto

Soy nuevo en Tikz y logré combinar varios ejemplos de código de Tikz [x] para representar un sistema de 3 grados de libertad. Sin embargo, me gustaría 'traducir'/mover el péndulo de masaMETROa la segunda misaM2pero no funciona. El centro del contenido del pdf parece estar definido en elM.centroy la "definición" de ángulo también. No logré cambiar eso cuando intenté mover el péndulo, el ángulo no se trasladará a la siguiente masa M2.

Vea el código a continuación:

\documentclass[tikz]{standalone}
\usetikzlibrary{calc,patterns,decorations.pathmorphing,decorations.markings}

\usepackage{physics}
\usepackage{siunitx}
\sisetup{detect-all} % to allow \pi in \SI
\usepackage{tikz,pgfplots}
\usepackage[outline]{contour} % glow around text
\usetikzlibrary{calc}
\usetikzlibrary{angles,quotes} % for pic
\usetikzlibrary{arrows.meta}
\tikzset{>=latex} % for LaTeX arrow head
\contourlength{1.2pt}

\colorlet{xcol}{blue!70!black}
\colorlet{vcol}{green!60!black}
\colorlet{myred}{red!70!black}
\colorlet{myblue}{blue!70!black}
\colorlet{mygreen}{green!70!black}
\colorlet{mydarkred}{myred!70!black}
\colorlet{mydarkblue}{myblue!60!black}
\colorlet{mydarkgreen}{mygreen!60!black}
\colorlet{acol}{red!50!blue!80!black!80}
\tikzstyle{CM}=[red!40!black,fill=red!80!black!80]
\tikzstyle{xline}=[xcol,thick,smooth]
\tikzstyle{mass}=[line width=0.6,red!30!black,fill=red!40!black!10,rounded corners=1,top color=red!40!black!20,bottom color=red!40!black!10,shading angle=20]
\tikzstyle{faded mass}=[dashed,linewidth=0.1,red!30!black!40,fill=red!40!black!10,rounded corners=1,top color=red!40!black!10,bottom color=red!40!black!10,shading angle=20]
\tikzstyle{rope}=[black!70!black,thick,line cap=round]
\def\rope#1{ \draw[black,line width=0.8] #1; \draw[rope,line width=1.1] #1; }
\tikzstyle{force}=[->,myred,very thick,line cap=round]
\tikzstyle{velocity}=[->,vcol,very thick,line cap=round]
\tikzstyle{Fproj}=[force,myred!40]
\tikzstyle{myarr}=[-{Latex[length=3,width=2]},ultra thick]
\def\tick#1#2{\draw[thick] (#1)++(#2:0.12) --++ (#2-180:0.24)}
\DeclareMathOperator{\sn}{sn}
\DeclareMathOperator{\cn}{cn}
\DeclareMathOperator{\dn}{dn}
\def\N{80} % number of samples in plots

\tikzstyle{axis}=[->,thick] %line width=0.6

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\tikzstyle{spring}=[thick,decorate,decoration={zigzag,pre length=0.3cm,post length=0.3cm,segment length=6,amplitude=1.75mm}] %amplitude=1.75mm
\tikzstyle{damper}=[thick,decoration={markings,  
  mark connection node=dmp,
  mark=at position 0.5 with 
  {
    \node (dmp) [thick,inner sep=0pt,transform shape,rotate=-90,minimum width=15pt,minimum height=3pt,draw=none] {};
    \draw [thick] ($(dmp.north east)+(2pt,0)$) -- (dmp.south east) -- (dmp.south west) -- ($(dmp.north west)+(2pt,0)$);
    \draw [thick] ($(dmp.north)+(0,-5pt)$) -- ($(dmp.north)+(0,5pt)$);
  }
}, decorate]
\tikzstyle{ground}=[fill,pattern=north east lines,draw=none,minimum width=0.75cm,minimum height=0.3cm,inner sep=0pt,outer sep=0pt]



\definecolor{monOrange}{RGB}{255,157,0}
\definecolor{monBleu}{rgb}{0.2,0.4,0.6}
\definecolor{monCyan}{RGB}{74,181,247}
\definecolor{monGris}{RGB}{100,100,100}
\definecolor{monRed}{RGB}{255, 36, 0}

\tikzset{
    seisme/.style={color=cyan,ultra thick,->},
        vent/.style={color=monRed,ultra thick,->},
    }   

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{document}


%%%%%%%%%%%%%%% SHEMA MODAL 3DDL %%%%%%%%%%%%%%%
\begin{tikzpicture}[scale=1.1, every node/.style={scale=1.3}]
% Rectangle masse m1 + petites roues
\node [draw, outer sep=0pt, thick] (M) [minimum width=2cm, minimum height=1.5cm] {$M$};
\draw [thick, fill=white] (M.south west) ++(0.2cm,-0.125cm) circle (0.125cm)  (M.south east) ++(-0.2cm,-0.125cm) circle (0.125cm);

% Rectangle masse m2 + petites roues
\node [draw, outer sep=0pt, thick] (M2) [minimum width=2cm, minimum height=1.5cm, xshift = 4cm] {$M_2$}; % rectangle entourant la masse m2
\draw [thick, fill=white] (M2.south west) ++(0.2cm,-0.125cm) circle (0.125cm)  (M2.south east) ++(-0.2cm,-0.125cm) circle (0.125cm); % 2 petits cercles sous la masse m2

% Ground bas
\node (ground) [ground,anchor=north,yshift=-0.2cm,minimum width=10cm,xshift=2.03cm] at (M.south) {}; % ground bas hachurage
\draw (ground.north west) -- (ground.north east) -- (ground.south east) -- (ground.south west); %traits horizontaux entourant le ground bas
\node (fill) [ground,xshift=-0.15cm,minimum height = 0.3cm, minimum width = 0.3cm] at (ground.west) {}; %petit ajout de ground bas tout à gauche
\draw (fill.north west) -- (fill.south west) -- (fill.south east);

% Ground vertical
\node (wall) [ground, rotate=-90, minimum width=3cm,anchor=south east] at (fill.north west) {}; % ground vertical hachurage
\draw (wall.north east) -- (wall.north west) -- (wall.south west) -- (wall.south east);  %traits horizontaux entourant le ground vertical

% % Ressort k
\draw [spring] (M.east) -- (M2.west) node (k) [midway,yshift=0.4cm] {$k$};

% Ressort k
\draw [spring] (wall.15) node[left= 0.3cm]{$O$} -- ($(M.north west)!(wall.15)!(M.south west)$) node [midway,yshift=0.4cm] {$k$};

% Force d'excitation sur la masse m2
%\draw [-latex,ultra thick] (M2.east) -- +(1cm,0cm) node [right] (u) {$F(t) = F_0 \sin{\omega t}$};

%Déplacement de la masse m1 noté y1
\draw [-latex,ultra thick] (M.center) ++(0cm, 1.4cm) -- +(1cm,0cm) node [above] (y1) {$x(t)$}; % flèche déplacement x(t)
\draw [dashed] (M.center) -- +(0cm,1.4cm); % trait pointillés y1

% Déplacement de la masse m2 noté y2
\draw [-latex,ultra thick] (M2.center) ++(0cm, 1.4cm) -- +(1cm,0cm) node [above] (y2) {$x_2(t)$}; % flèche déplacement x(t)
\draw [dashed] (M2.center) -- +(0cm,1.4cm); % trait pointillés y2

% Axes (x,y) et centre 0 du repère cartésien
%\draw[axis] (0,0)--(5.7,0) node[right] {$\overrightarrow{x}$}
\draw[dashed,->](M2)--(7.7,0) node[right]{$\overrightarrow{x}$};
\draw[dashed,->](wall.15)--(-3.5,5) node[left]{$\overrightarrow{y}$};

% PENDULUM
\def\L{5}  % string length
\def\ang{28} % angle string
\def\R{0.4} % ball radius
\def\F{1.0}  % force magnitude
  \coordinate (M) at (\ang-90:\L);
  \coordinate (M') at (0,-\L);
  \coordinate (O) at (0,0);
  \coordinate (B) at (0,-\L-2.2*\R);
  \coordinate (FT) at ($(M)+(90+\ang:{\F*cos(\ang)+\R})$);
  \coordinate (FG) at ($(M)+(-90:{\F+\R})$);
  \coordinate (FGx) at ($(M)+(-90+\ang:{0.55*\F+\R})$);
  \coordinate (MA) at ($(M)+(180+\ang:{\F*sin(\ang)+\R})$);
  %\draw[faded mass] (M') circle(\R);
  \draw[dashed] (O) -- (B);
  \draw[dashed] (-90+\ang+10:\L) arc(-90+\ang+10:-110:\L) (B);
  \rope{(O) -- (M)} \path (O) -- (M) node[midway,above right=-1] {$L$};
  \fill[black] (O) circle(0.04);
  \draw[mass] (M) circle(\R) node {$m$};
  \draw pic[myarr,"$\theta$",xcol,draw=xcol,angle radius=43,angle eccentricity=1.30] {angle=B--O--M};


\end{tikzpicture}



\end{document}

Esto es lo que obtengo: Sistema de 3 grados de libertad.

¡Cualquier sugerencia será bienvenida!

Código fuente de Pendulum TikZ

Código fuente del sistema tierra-masa-resorte

Respuesta1

Para divertirse, el resultado de la simulación animada.

Las ecuaciones de movimiento se han derivado de las energías cinética y potencial del sistema mediante laFormalismo de Lagrangey resuelto con \pstODEsolvedel paquetepst-ode. ingrese la descripción de la imagen aquí ingrese la descripción de la imagen aquí

%\documentclass[margin=3pt,10pt,export]{standalone} % for GIF
%\documentclass[margin=3pt,10pt,dvisvgm]{standalone} % for SVG, run twice: dvilualatex example ; dvisvgm --font-format=woff --zoom=-1 --page=1 example.dvi
\documentclass[margin=3pt,10pt]{standalone} % for PDF, run lualatex twice
 
\usepackage{pst-ode}
\usepackage[loop,controls]{animate} 
\usepackage{tikz} 
\usetikzlibrary{calc,arrows.meta,decorations.pathmorphing,patterns.meta}
\usepackage{listofitems} % read space separated items 
\usepackage[T1]{fontenc} 
\usepackage{xsavebox} 
 
% adjustable parameters & definitions 
\pstVerb{
tx@Dict begin % all definitions within PSTricks dict 
  /tEnd 60 def      % time span to be simulated [s]
%  /tEnd 13.56 def   % this time span gives a nearly cyclic impression, suitable for GIF
  /m1 1 def         % mass_1 [kg] 
  /m2 1 def         % mass_2 [kg] 
  /m3 0.1 def       % mass_3 (bob) [kg]
  /L 2 def          % pendulum length [m] 
  /k1 80 def        % spring constant [kg/s^2] 
  /k2 40 def        % spring constant [kg/s^2] 
  /g 9.81 def       % acceleration [m/s^2] 
  /x2Zero 0.9 def   % initial displacement of mass_2 [m] 
  /thetaZero 0 def  % initial displacement of pendulum from vertical [°] 
  %  
  % (integer) number of time steps (for 25 frames per s) + 1 
  /N (cvi(tEnd*25+1)) AlgParser cvx exec def
  %
  % initial displacement of mass_1
  /x1Zero (k2/(k1+k2)*x2Zero) AlgParser cvx exec def
  %
  % some constants 
  /k12M1 ((k1+k2)/m1) AlgParser cvx exec def
  /k2M1  (k2/m1)      AlgParser cvx exec def
  %
  % displacements of mass_1, mass_2, pendulum
  /x1    (x[0]) AlgParser cvx def
  /x2    (x[1]) AlgParser cvx def
  /theta (x[2]) AlgParser cvx def
  %
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  % 1st order ODE system (equations of motion) 
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  % velocities
  /v1    (x[3]) AlgParser cvx def
  /v2    (x[4]) AlgParser cvx def
  /omega (x[5]) AlgParser cvx def
  % accelerations
  /a1    (k2M1*x2 - k12M1*x1) AlgParser cvx def
  /a2    ((m3*sin(theta)*(g*cos(theta)+L*omega^2)-k2*(x2-x1))/(m2+m3*sin(theta)^2)) AlgParser cvx def
  /alpha (-(a2*cos(theta) + g*sin(theta))/L) AlgParser cvx def
end
}
 
% solve equations of motion 
\pstODEsolve[algebraicAll,saveData]{timeX1X2Theta}{    % PS variable and file (base-)name that take result list 
  t | x1 | x2 | RadtoDeg(theta-TwoPi*cvi(theta/TwoPi)) % table format of data to be saved in timeX1X2Theta(.dat)
}{0}{tEnd}{N}{                                         % t_0, t_end, number of  time steps + 1 
  x1Zero | x2Zero | DegtoRad(thetaZero) | 0 | 0 | 0    % initial conditions (displacements, velocities)
}{ 
  v1 | v2 | omega | a1 | a2 | alpha                    % ODE system's RHS 
} 
 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
% \fileopenr{<file stream>}{<file name>}, opens file for reading 
\newcommand\fileopenr[2]{% 
  \newread#1% 
  \immediate\openin#1=#2% 
} 
% \readtolist[<sep char>]{<file stream>}{\list} 
% reads a line from file stream and splits at <sep char> into \list[1], \list[2], ... 
\newcommand\readtolist[3][,]{{% 
  \setsepchar{#1}% 
  \immediate\read#2 to \inputline% 
    \ifeof#2 
      \immediate\closein#2% 
      \ifdefined\multiframebreak\multiframebreak\fi% 
    \else% 
      \greadlist*#3\inputline% 
    \fi% 
}} 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 

\tikzset{spring/.style={decorate, decoration={zigzag,pre length=0.2cm,post length=0.2cm,segment length=\dimexpr(#1-0.4cm-1pt)/14\relax, amplitude=0.1cm}}}

\begin{document}
\IfFileExists{timeX1X2Theta.dat}{}{dummy\end{document}}%
% cart
\begin{xlrbox}{cart}
  \begin{tikzpicture}[line width=0.2mm]
    \useasboundingbox (-1,0) rectangle (1,1.6);
    \draw (-0.99,0.1) rectangle (0.99,1.59);
    \fill [radius=0.1] (0,0.8) -- ++(0.1,0) arc [radius=0.1,start angle=0,end angle=90] -- ++(0,-0.2) arc [start angle=270, end angle=180];
    \draw [thin] (0,0.8) circle [radius=0.1];
    \filldraw [fill=white] (-0.8,0.1) circle [radius=0.08] (0.8,0.1) circle [radius=0.08];
  \end{tikzpicture}
\end{xlrbox}%
%
\begin{animateinline}{25}
  \fileopenr{\data}{timeX1X2Theta.dat}%
  \readtolist[ ]{\data}{\table}%
  \multiframe{10000}{}{
    \begin{tikzpicture}[line width=0.2mm]
      \useasboundingbox (-0.3,-1.5) rectangle (10.1,3.1);
      % ground & wall
      \draw [pattern={Lines[angle=-45,line width=0.2pt,distance={3pt/sqrt(2)}]}] (0,0) -- (10,0) -- (10,-0.25) -- (-0.25,-0.25) -- (-0.25,2) -- (0,2) --cycle;  
      % cart 1
      \path [shift={(\table[2],0)}] (3,0.8) node[inner sep=0, name={cart1}] {\thecart} node [anchor=south] {$m_1$};
      % mass_2 (cart2) and mass_3 (bob) centres
      \path[shift={(\table[3],0)}] (7,0.8) coordinate (mass2) ++(\fpeval{\table[4]-90.0}:2) coordinate (bob);
      % cart 2
      \path (mass2) node[inner sep=0] (cart2) {\thecart} node [anchor=south] {$m_2$};
      % springs
      \coordinate (wall) at (0,0.8);
      \draw[line join=round, line cap=rect] let \p1=($(cart1.west)-(wall)$) in [draw,spring={\x1}] (wall) -- (cart1.west) node [midway,above,yshift=1pt] {$k_1$};
      \draw[line join=round, line cap=rect] let \p1=($(cart2.west)-(cart1.east)$) in [draw,spring={\x1}] (cart1.east) -- (cart2.west) node [midway,above,yshift=1pt] {$k_2$};
      % pendulum
      \draw (mass2) -- (bob) node[inner sep=1pt,midway,anchor=west,rotate={\table[4]}] {$L$};
      \draw [thin,fill=white] (mass2) circle [radius=0.03];
      \draw [thin,fill=white!90!black] (bob) circle [radius=0.21];
      \path (bob) node[rotate={\table[4]}] {\scriptsize $m_3$};
      % coordinates
      \draw[very thin,dashdotted] (3,0.8) -- ++(0,1); \draw[-latex] (3,0.8) ++(0,1) -- ++(0.5,0) node[above] {$x_1$};
      \draw[very thin,dashdotted] (7,0.8) -- ++(0,1); \draw[-latex] (7,0.8) ++(0,1) -- ++(0.5,0) node[above] {$x_2$};
      \draw[very thin,dashdotted] (mass2) -- ++(0,-0.55);
      \draw[-latex] (mass2) ++(0,-0.5) arc [radius=0.5,start angle=270,end angle=300] -- ++(30:0.1) node[inner sep=0pt,above right] {\small $\theta$};
    \end{tikzpicture}%
    \readtolist[ ]{\data}{\table}
  }
\end{animateinline}
\end{document}

Respuesta2

Probablemente, la forma más sencilla sea simplemente shiftcodificar el péndulo mediante (M2).

péndulo desplazado

Limpié, minimizé y actualicé parcialmente su código, además de arreglarlo para evitar errores.

\documentclass[border=5pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{calc,patterns,angles,quotes,arrows.meta,decorations.pathmorphing}
\tikzset{>=latex} % for LaTeX arrow head

\colorlet{xcol}{blue!70!black}

\tikzset{mass/.style={line width=0.6,red!30!black,fill=red!40!black!10,rounded corners=1,top color=red!40!black!20,bottom color=red!40!black!10,shading angle=20}}
\tikzset{rope/.style={black!70!black,thick,line cap=round}}
\tikzset{force/.style={->,myred,very thick,line cap=round}}
\tikzset{myarr/.style={->,ultra thick}}

\newcommand\rope[1]{ \draw[black,line width=0.8] #1; \draw[rope,line width=1.1] #1; }

\tikzset{spring/.style={thick,decorate,decoration={zigzag,pre length=0.3cm,post length=0.3cm,segment length=6,amplitude=1.75mm}}, %amplitude=1.75mm
  damper/.style={thick,decoration={markings,  
      mark connection node=dmp,
      mark=at position 0.5 with 
      {
        \node (dmp) [thick,inner sep=0pt,transform shape,rotate=-90,minimum width=15pt,minimum height=3pt,draw=none] {};
        \draw [thick] ($(dmp.north east)+(2pt,0)$) -- (dmp.south east) -- (dmp.south west) -- ($(dmp.north west)+(2pt,0)$);
        \draw [thick] ($(dmp.north)+(0,-5pt)$) -- ($(dmp.north)+(0,5pt)$);
      }
    }, decorate},
  ground/.style={fill,pattern=north east lines,draw=none,minimum width=0.75cm,minimum height=0.3cm,inner sep=0pt,outer sep=0pt},
}   

\begin{document}
%%%%%%%%%%%%%%% SHEMA MODAL 3DDL %%%%%%%%%%%%%%%
\begin{tikzpicture}[scale=1.1, every node/.style={scale=1.3}]
  % Rectangle masse m1 + petites roues
  \node [draw, outer sep=0pt, thick] (M) [minimum width=2cm, minimum height=1.5cm] {$M$};
  \draw [thick, fill=white] (M.south west) ++(0.2cm,-0.125cm) circle (0.125cm)  (M.south east) ++(-0.2cm,-0.125cm) circle (0.125cm);
  
  % Rectangle masse m2 + petites roues
  \node [draw, outer sep=0pt, thick] (M2) [minimum width=2cm, minimum height=1.5cm, xshift = 4cm] {$M_2$}; % rectangle entourant la masse m2
  \draw [thick, fill=white] (M2.south west) ++(0.2cm,-0.125cm) circle (0.125cm)  (M2.south east) ++(-0.2cm,-0.125cm) circle (0.125cm); % 2 petits cercles sous la masse m2
  
  % Ground bas
  \node (ground) [ground,anchor=north,yshift=-0.2cm,minimum width=10cm,xshift=2.03cm] at (M.south) {}; % ground bas hachurage
  \draw (ground.north west) -- (ground.north east) -- (ground.south east) -- (ground.south west); %traits horizontaux entourant le ground bas
  \node (fill) [ground,xshift=-0.15cm,minimum height = 0.3cm, minimum width = 0.3cm] at (ground.west) {}; %petit ajout de ground bas tout à gauche
  \draw (fill.north west) -- (fill.south west) -- (fill.south east);
  
  % Ground vertical
  \node (wall) [ground, rotate=-90, minimum width=3cm,anchor=south east] at (fill.north west) {}; % ground vertical hachurage
  \draw (wall.north east) -- (wall.north west) -- (wall.south west) -- (wall.south east);  %traits horizontaux entourant le ground vertical
  
  % % Ressort k
  \draw [spring] (M.east) -- (M2.west) node (k) [midway,yshift=0.4cm] {$k$};
  
  % Ressort k
  \draw [spring] (wall.15) node[left= 0.3cm]{$O$} -- ($(M.north west)!(wall.15)!(M.south west)$) node [midway,yshift=0.4cm] {$k$};
  
  % Force d'excitation sur la masse m2
  %\draw [-latex,ultra thick] (M2.east) -- +(1cm,0cm) node [right] (u) {$F(t) = F_0 \sin{\omega t}$};
  
  %Déplacement de la masse m1 noté y1
  \draw [-latex,ultra thick] (M.center) ++(0cm, 1.4cm) -- +(1cm,0cm) node [above] (y1) {$x(t)$}; % flèche déplacement x(t)
  \draw [dashed] (M.center) -- +(0cm,1.4cm); % trait pointillés y1
  
  % Déplacement de la masse m2 noté y2
  \draw [-latex,ultra thick] (M2.center) ++(0cm, 1.4cm) -- +(1cm,0cm) node [above] (y2) {$x_2(t)$}; % flèche déplacement x(t)
  \draw [dashed] (M2.center) -- +(0cm,1.4cm); % trait pointillés y2
  
  % Axes (x,y) et centre 0 du repère cartésien
  %\draw[axis] (0,0)--(5.7,0) node[right] {$\overrightarrow{x}$}
  \draw[dashed,->](M2)--(7.7,0) node[right]{$\overrightarrow{x}$};
  \draw[dashed,->](wall.15)--(-3.5,5) node[left]{$\overrightarrow{y}$};
  
  % PENDULUM
  \def\L{5}  % string length
  \def\ang{28} % angle string
  \def\R{0.4} % ball radius
  \def\F{1.0}  % force magnitude
  \begin{scope}[shift=(M2)]
    \coordinate (Mx) at (\ang-90:\L);
    \coordinate (M') at (0,-\L);
    \coordinate (O) at (0,0);
    \coordinate (B) at (0,-\L-2.2*\R);
    \coordinate (FT) at ($(Mx)+(90+\ang:{\F*cos(\ang)+\R})$);
    \coordinate (FG) at ($(Mx)+(-90:{\F+\R})$);
    \coordinate (FGx) at ($(Mx)+(-90+\ang:{0.55*\F+\R})$);
    \coordinate (MA) at ($(Mx)+(180+\ang:{\F*sin(\ang)+\R})$);
    \draw[dashed] (O) -- (B);
    \draw[dashed] (-90+\ang+10:\L) arc(-90+\ang+10:-110:\L) (B);
    \rope{(O) -- (Mx)} \path (O) -- (Mx) node[midway,above right=-1] {$L$};
    \fill[black] (O) circle(0.04);
    \draw[mass] (Mx) circle(\R) node {$m$};
    \draw pic[myarr,"$\theta$",xcol,draw=xcol,angle radius=43,angle eccentricity=1.30] {angle=B--O--Mx};
  \end{scope}
\end{tikzpicture}

\end{document}

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