Purpose: To demonstrate precession, nutation and gyroscopic stability.

Air-suspended spherical ball with axle for an eccentric spinner; balance ring; and piece of string.

Without the spinner in place, the top is nearly a symmetric sphere and the axle will stay pointed in one direction, even though the table is moved or rotated. With the spinner in place (near the free end of the axle), precession and nutation can be demonstrated. As the top spins slower, the length of the nutation cycle increases and the precession rate is faster. As the top spins faster, the precession rate is slower and the amplitude and period of the nutation cycle both decrease. The nutation may be inhibited by careful hand adjustment of the axle or it may be enhanced by giving the axle tip a push.

Forcing the spinner rim to touch against the air suspension table gets the axle to move in the opposite sense from the precession. Other attachments are available for your enlightenment and amusement.

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