\PassOptionsToPackage{table}{xcolor}
\documentclass{article}
\usepackage{siunitx,ragged2e,booktabs,lipsum,adjustbox}
\usepackage[usestackEOL]{stackengine}
\begin{document}
    \tabcolsep0pt
    \rowcolors{2}{gray!20}{}
    \begin{tabular}{
            >{\RaggedRight}m{0.5\linewidth}>{\Centering}m{0.2\linewidth}
        }
            \toprule
        Parameter                          & Symbol \\
        \midrule
        DC Motor  Rotor Inertia            & $J_M$\\ %
        DC Motor Rotor Damping Coefficient & $D_M$\\
        Supply Voltage                      & $V_S$\\
        DC Motor  Rotor Inertia            & $J_M$\\ %
        DC Motor Rotor Damping Coefficient & $D_M$\\
        Supply Voltage                      & $V_S$\\
        \bottomrule
    \end{tabular}
\end{document}