Dragging a ball introduces energy into the system. Observe how that energy passes from one ball to another.
In this simulation, the ball moves describing a circular horizontal path. Observe what happens as the period varies. Is there an equilibrium of forces?
Foucalt's pendulum is a device invented by the French scientist Leon Foucault to test the rotation of the Earth.
Mechanics, Part 1
Advanced Fluid Mechanics 1: Fundamentals