% \graphset{A}{\addplot...}{\addplot...}
\newcommand{\graphset}[3]{
  \begin{figure}[!ht]
  \centering

  \pgfplotsset{
        ymin={-1.2}, ymax={1.2},
        xmin={-0.2}, xmax={3.2},
        width=2.5in, height=1.3in,
        xlabel={T},
        ytick={-1,0,1},
        xmajorticks=false,
        axis x line=bottom,
        axis y line=left,
  }

  \begin{minipage}{.5\textwidth}
    \centering
    \begin{tikzpicture}
    \begin{axis}[
        title={Distance/Time Plot #1},
        ylabel={X},
    ]
    #2
    \end{axis}
    \end{tikzpicture}
  \end{minipage}%
  \begin{minipage}{.5\textwidth}
    \centering
    \begin{tikzpicture}
    \begin{axis}[
        title={Velocity/Time Plot #1},
        ylabel={V},
    ]
    #3
    \end{axis}
    \end{tikzpicture}
  \end{minipage}
  \end{figure}
}

\subsection{Trial A}
\graphset{A}{
  \addplot[draw=black][domain=0:3]{0.5};
}{
  \addplot[draw=black][domain=0:3]{0};
}
In example A, the object does not move. Its position is constant, and its velocity is 0. To create this motion, the cart was placed on the track and not moved.