1J20.70 Rolling Uphill (Double Cone on Incline)


Centre-of-mass, gravitational potential energy


A symmetrical double cone piece is positioned on the narrow end of a triangular track with a slight incline at the other end. The shape of the track and the pitch of the cones are such that the centre-of-mass of the double cone is at its lowest point at the highest part of the track. As the cone rolls to lower its centre-of-mass, the piece appears to roll uphill on the track.



  • [1] Triangular track
  • [1] Metal cylinder
  • [1] Double cone

Classroom Assembly

  1. Place the triangular track on a horizontal surface.
  2. Be sure to check that there are no other objects present that may affect double cone's direction of motion.

Important Notes

  • Catch the metal cylinder that is rolling down the track before it hits the end of the track


  1. Release metal cylinder at the widest part of the track as a control experiment.
  2. Release the double cone at the widest part of the track. Nothing should happen.
  3. Release double cone at the narrow end of the track, see how it counterintuitively rolls uphill.


Additional Resources


  • PIRA 1J20.70


  • Don't attempt this at home!

Last revised

  • 2020


Related AV

Related demos


If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.