\begin{eqnarray*}
    y_{res}(t)&=& y_1(t) + y_2(t) \\ 
    &=& \hat{y}(\sin(2\pi f_1 t) + \sin(2 \pi f_2 t))   \\ 
    &=& 2\hat{y} \cos(2\pi \frac{f_1 - f_2}{2}t) \cdot \sin(2\pi \frac{f_1 + f_2}{2}t)
\end{eqnarray*}

\begin{eqnarray*}
    f_s = \frac{f_1 - f_2}{2} \\
        = \frac{\frac{\omega_1 - \omega_2}{2\pi}}{2} \\
    T	= \frac{4\pi}{\omega_2 - \omega_1}
\end{eqnarray*}

\[ \omega_1 = \sqrt{\frac{D}{m}} = 2 \pi f = \frac{2 \pi}{T} \]
\[ T = 2 \pi \sqrt{\frac{m}{D}} \]

$ F_G = F_{Rückstell} $