% ---------------------------------------------------------------
% Sistema massa-mola-amortecedor
% Bibliotecas (carregadas no chunk .qmd):
%   arrows.meta, positioning, calc, decorations.pathmorphing, patterns
% ---------------------------------------------------------------
\begin{tikzpicture}[>=Latex, line width=0.9pt]

  % --- Parede fixa ---
  \fill[pattern=north east lines] (-0.45,-1.6) rectangle (0,1.6);
  \draw[line width=1.3pt] (0,-1.6) -- (0,1.6);

  % --- Massa ---
  \def\mx{4.4}
  \draw[fill=blue!8, line width=1pt] (\mx,-1.05) rectangle (\mx+1.8,1.05);
  \node at (\mx+0.9,0) {\large $m$};

  % --- Mola (ramo superior) ---
  \draw[decorate, decoration={coil, aspect=0.6, segment length=7pt, amplitude=7pt}]
        (0,0.55) -- (\mx,0.55);
  \node at (\mx/2,1.15) {$k$};

  % --- Amortecedor (ramo inferior) ---
  \draw (0,-0.55) -- (1.5,-0.55);
  \draw (1.5,-0.95) rectangle (2.25,-0.15);
  \draw[line width=1.1pt] (1.95,-0.85) -- (1.95,-0.25);
  \draw (1.95,-0.55) -- (\mx,-0.55);
  \node at (\mx/2,-1.15) {$b$};

  % --- Força de entrada ---
  \draw[->, red!75!black, line width=1.3pt]
        (\mx+1.8,0) -- (\mx+3.2,0) node[midway, above] {$u(t)$};

  % --- Deslocamento ---
  \draw[->] (\mx+0.9,1.45) -- (\mx+2.05,1.45) node[midway, above] {$y(t)$};

  % --- Solo ---
  \fill[pattern=north east lines] (-0.45,-1.9) rectangle (\mx+3.4,-1.6);
  \draw[line width=1.3pt] (-0.45,-1.6) -- (\mx+3.4,-1.6);

\end{tikzpicture}