Fading Motion

A swinging pendulum pours sand from its bob onto a variable-speed conveyor belt which moves in a direction perpendicular to the swing of the pendulum. The sand forms a wavy pattern on the belt which diminishes in amplitude exponentially due to a damping mechanism consisting of a paddle moving through thick oil. The oil reservoir may be raised or lowered (the paddle is fixed to the pendulum) to vary the amount of damping.