This 2D simulator models a dropped slinky as a vertical chain of point masses connected by springs, integrated with real Newtonian dynamics rather than a scripted animation. Before release the chain sits in its static hanging equilibrium, with each spring stretched exactly enough to support the weight below it; the moment you hit Drop, the top is freed but the rest of the chain keeps its pre-drop tension pattern for an instant, so the bottom coil stays almost motionless while a compression wave races down from the top and only sets each coil falling once it arrives. Watch the live readouts to see the center of mass fall smoothly at g throughout, even while the bottom coil's motion is delayed and abrupt — and adjust spring stiffness or coil count to see how a stiffer or shorter slinky changes how fast that wave reaches the bottom.