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          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.
         
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