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A limited number of time steps are used in the solution. For large drop heights, low damping and stiff springs the drop response will be multiple low damped bounces and the animation will likely stop during a mid bounce. For smaller drop heights, moderate to high damping (>10%) and soft springs (fn < 10-20 Hz) the drop response will be one to a few rebounds and the animation will likely stop at the static deflection of W/k.