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Home/Classical Mechanics/Rattleback (celt)

Rattleback (celt)

Chiral hull couples spin and rocking in a toy ODE: one rotation sense reverses after growing wobble.

Toy parameters

7 rad/s
1

Flip chirality to swap which initial spin is “stable”. Live ω is drawn on the canvas.

About this model

A rattleback (celt) spins smoothly one way but wobbles and can reverse when spun the other — a signature of chiral geometry and friction coupling spin to rocking modes. This simulator is an intentional cartoon: a small coupled ODE ties spin rate to lateral rocking so students can see how “wrong-handed” rotation feeds energy into oscillation. It is not a full asymmetric-top integrator with realistic contact patches.

Who it's for: Introductory rigid-body curiosity demos; pair with a real tabletop celt if available.

Key terms

  • Rattleback
  • Chirality
  • Spin reversal
  • Friction coupling
  • Toy model

How it works

A rattleback’s curved footprint couples spin and sideways rocking. This is a cartoon ODE, not a full rigid-body integrator — use it to show why one rotation sense dies out and flips.

Frequently asked questions

Can I read quantitative reversal times from this page?
Only qualitatively. Parameters are tuned for visible reversal on a laptop screen, not calibrated to a specific celts dimensions or μ.
What should I say in class about the real toy?
Mention that curvature asymmetry and sliding vs rolling at the contact line matter; many articles derive conditions for instability of steady spin about the intermediate axis of inertia.