Guinea and feather tube apparatus with 6 induction coils connected in series. When a bar magnet (included in the scope of delivery) is dropped in the tube, a voltage is induced as it passes each of the respective coils. Due to the magnet's free-fall acceleration caused by gravity, the voltage peaks increase proportionally with the time (speed proportional to time), and the time intervals between the voltage peaks become ever shorter. The voltage characteristic can be plotted using any conventional storage oscilloscope or with a computer interface.