1D50.45 Coin on a Coathanger

Concepts

Forces in circular motion

Overview

A coin is balanced on the hook end of a coathanger. When the coathanger is swung in a full circle, the coin does not fall off. The penny will not be visible from far away, but observers can hear the sound it makes when the coathanger slows and the coin strikes the ground or wall.

Details

Equipment

  • [1] Coin
  • [1] Swing made from a stretched coathanger

Important Notes

  • This demonstration requires a lot of advance practice. Confidence and a smooth motion are required.
  • Try not to hit anyone with the penny if it flies off, and try to find it afterwards.

Script

  1. Place your finger in the bend of the coathanger opposite to the hook.
  2. Carefully balance the coin on the hook of the coathanger.
  3. Swing the coathanger vertically, starting with a low amplitude and working up to large amplitudes.
  4. Continue to increase the amplitude of the swing until the coathanger swings in a full circle.

 

Additional Resources

References

  • PIRA 1D50.45
  • Video Encyclopedia 05-18 
  • J. Dixon "A Penny for your Thoughts" TPT4, 38 (1966) 
  • G.W. Ficken "Putting a penny into orbit" AJP40(5), 776 (May 1972) 
  • P. Salmons "The penny and the coathanger" TPT15(1), 46 (Jan 1977) 
  • A variation, in which the coin is balanced on the long edge of an undistorted hanger, is described by Sutton M-155 and Miller p63 

Disclaimer

  • Don't attempt this at home!

Last revised

  • 2018

Technicals

  • Original construction: the coathanger was stretched to form a diamond shape with one bend directly opposite the hook. The end of the hook was filed flat.
  • Any coin can be used. A penny works well. A slightly-drilled penny is available to make this demo easier.

Related AV

Related demos

  • Pail of Water
  • Waiter's Tray

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.