Passage IV

The following experiments were done to study factors that affect the precession of a top. Precession is the revolution of a top around an imaginary line perpendicular to the surface at the point of contact (see Figure 1).

Experiment 1

An electric motor was attached to a top and used to give the top a known spin rate or number of revolutions per minute (rpm). Once the desired spin rate was achieved, the motor was removed and the number of precessions per minute was counted. The process was repeated using different spin rates. The results are recorded in Table 1.

Experiment 2

The distance from the surface to the top's center of gravity (r) was varied by changing the length of the light-weight stem on the top from Experiment 1. The electric motor was used to generate the same spin rate in each trial. The measured precession rate is given in Table 2.

Experiment 3

A scientist took the top from Experiment 1 to the Moon. It was found that for a given spin rate and stem length, the precession rate was approximately one-sixth that on Earth. For example, a precession rate of 12 rpm on Earth would be approximately 2 rpm on the Moon.