/Pendulum

Mathematical pendulum with friction, modeled by the Newton equation $$ \ddot{\theta} = - \omega^2 \, \sin (\theta) - \beta \ell \dot{\theta} $$ with frequency \( \omega = \sqrt{G/\ell} \) and some small friction coefficient \( \beta \). You can change the lenght \( \ell \) moving the red ball.