08 Precession (3a)

08 Precession (3a)#

Aim#

To show how a rotating wheel reacts to an applied torque.

Subjects#

  • 1Q50 (Gyros)

Diagram#

../../../../../_images/figure_0111.png

Fig. 255 .#

Equipment#

  • bicycle wheel with handles

  • 1 piece of rope

  • 1 stick

Presentation#

The wheel is rotating and held by a string. The rotating wheel has an angle of about \(45^{\circ}-60^{\circ}\) with the vertical. The wheel will precess about a vertical axis. When the instructor pushes with the side of his hands or a stick against one of the handles of the wheel in the direction of precession, then the rotating wheel will rise to a more vertical position. This can be continued, even passing the vertical.

Explanation#

The rotating wheel will precess due to gravitational torque, \(m g s\) ( \(I \omega_{0}\) moves in the direction of this gravitational torque; precession) (see Figure 256a).

../../../../../_images/figure_183.png

Fig. 256 .#

\(F\) is the applied force in the direction of precession (see Figure 256b). The applied torque is pointing vertically upward, so now \(I \omega_{0}\) moves also upward.

Sources#

  • Freier, George D. and Anderson, Frances J., A demonstration handbook for physics, pag. M-53

  • Sutton, Richard Manliffe, Demonstration experiments in Physics, pag. 79

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