Run the pendulum model for a much longer time than just 10 seconds (easy to change in the code above). You might find that the mass on the string starts to misbehave in certain ways. See if you ...

Simple harmonic motion describes ... gives the pendulum a tiny nudge that is sufficient to overcome the damping effect of mechanical friction and air resistance and maintain the pendulum’s ...

How Does Foucault’s Pendulum ... As it moved back and forth—facilitated by an electromagnetic push to keep it continuously swinging despite air resistance ... so the story isn’t that simple.