Determine the nonlinear ODE modeled by the Simulink diagram shown above.
\begin{itemize}
\item Use ONLY the following symbolic variables and functions (though you do not have to use them all): y, u, sin(), and sqrt().
\item These symbolic variables and functions are case sensitive (e.g. A \(\neq\) a, etc.).
\item Include mathematical operators (*, /, +, -, etc.) as appropriate between variables (e.g. A*cos(b*t) \(\neq\) Acos(bt), etc.)
\end{itemize}
$\frac{d^2y}{dt^2} = $