The can that rolls back

Materials and mounting instructions: A can with removable cap, a robust rubber cord of lenght abbout twice tha of the can, a heavy nut. Make two holes near the centres both of the botton of the can and of the removable cap. Pass the rubber band trough the heavy nut and then trough th holes of the bottom and of the cap, connecting the two ends in such a way from a lopp with the heavy nut hanging in the middle, as show in picture.
How to play: Launch the can trying to make it roll smoothlyon the floor. It will show down, stop and invert the motion: with smoothflor, two or three inversions of motion can be observed.
  • energy transfer: from the hands to the can
  • energy transformation: the translational kinetic energy given to the can is transformed in rotational kinetic energy of the can and in elastic torsional energy of the rubber band, sibce, while the can rolls, the heavynut does not rotate and the rubber band winds up, when the band is completely twisted, the elastic torsional energy is transformed back into rotational and translational kinetic energy,
  • energy storage: as elastic energy in the rubber band while it is being twisted,
  • the larger the initial energy given tp the can, the greater is the distance the can rolls before inverting the motion.
Educational aspects:
  • discover different forms of energy and transformations of energy (Eb)
  • experiment transfer of energy (Ec)
  • experiment storage of energy (Ed)
  • measure the distance covered by the can before inverting the motion (Sa)
  • compare with your expectations
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Last modified: Thu Nov 16 08:48:39 CET 2000