Description: A coin is balanced on the tip of a stretched coathanger which is then whirled about a finger.

Use the pre stretched coathanger or bring in your own and stretch it in class. If the latter check before the lecture that the tip of the hanger is flat. Stretch the hanger in such a way that the tip of the hanger points towards the center of swing.

Make a few practice rotations of the hanger to limber up the fingers and ensure no sticking. Balance the coin and whirl the hanger. With practice it is not difficult to stop the hanger without the coin flying off.

Cautions: This demonstration requires much practice.

Concepts demonstrated: forces in circular motion

Setup Time: Short

Difficulty/Commitment: Straightforward, after practice

Visibility: reasonably visible

Related demonstrations:

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
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