To demonstrate precession i.e. a rotating body is said to precess when, as a result of an applied couple, the axis of which is at right angles to the rotation axis, the body turns about the third mutually perpendicular axis.
- Rotating stool
- A.C. motor (Gyro-spinner)
A bicycle wheel weighted with lead on its rim is spun by a motorized wheel spinner and supported by a wire connected to a protruding axle. The gravitational torque causes precession of the wheel.
Demonstration 2 The spinning bicycle wheel is handed to a volunteer seated on the stool. When the wheel is raised overhead the student rotates through 90°. Lowering the wheel to its original position causes rotation in the other direction.
An electrically driven gyroscope has been mounted so that weights may be added to the protruding axles. If equal weights are placed equidistant from the rotating mass, no precession occurs; when an unbalanced torque exists the gyroscope rotates perpendicular to both the rotation axis and the couple axis.
Various gyroscopes are available to demonstrate principles of the gyroscope, including precession and rigidity in space.