An inverted pendulum is in unstable equilibrium..  left to itself, it will topple out of equilibrium.

However, if you apply a vibration with a suitably high frequency to the base of the pendulum, you can stabilize it.

Try it here.  ω is proportional to the frequency.  A value of 1 does not stabilize the pendulum.  What value does?

This is one of the 77 physical paradoxes in Mark Levi’s book Why Cats Land on their Feet.