Equipment: A 'swing' made from a stretched coathanger and a coin.

What it does: The coin is balanced on the hook end of the coathanger. When the coathanger is swung in a full circle, the coin does not fall off.

Concepts Demonstrated: Forces in circular motion.

Classroom assembly:

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.

Cautions: This demonstration requires a lot of advance practice. Confidence and a smooth motion are requried.

Setup Time: Short.

Difficulty: Straightforward after practice.

Visibility: High. This demonstration is appropriate for large lecture halls.

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

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.