Waterfall: Falling-Droplet Drag & Energy Physics (2D)

This 2D companion strips the 3D waterfall down to the mechanic that actually shapes it: a representative droplet's fall is integrated with RK4 through gravity and quadratic air drag, so its speed climbs toward — and never quite reaches — the analytic terminal velocity set by its own radius, the local gravity and the turbulence multiplier. A live v(t) graph and an energy panel that splits potential energy into kinetic energy at impact versus heat lost to drag make the fall's physics directly readable instead of merely decorative.