Technical Data - 3B SCIENTIFIC PHYSICS 8403000 Instructions D'emploi

2.1.2 Measurement of the angle of precession
The angular velocity of the pendulum's precession ω is
ω = ω · sin θ
e
ω
where = angular velocity of the earth
e
(= 360°/day = 15°/hour) and
θ = latitude of the place of experimentation.
In temperate latitudes, the pendulum swings at approx.
8°-13° per hour. By virtue of its measuring scale (see
Fig. 5), Foucault's pendulum allows measurements to
a)
Fig. 5: Angular measurement by shadow projection (swing of the pendulum observed from above)
2.1.3 Preventing elliptical motion of the pendulum
During the experiment, the pendulum must swing in
one and the same plane (Fig. 6b). If the pendulum beg-
ins to swing in an elliptical fashion (Fig. 6c), other factors
apart from the rotation of the earth have an influence
on its rotational motion. Accurate measurements are
therefore not possible.
In order to prevent elliptical motion, a ring is used in
Foucault's pendulum (see Fig. 2). At an ideal amplitude
setting, the ring has no influence on the plane of the
pendulum. It does, however, suppress any component
of the motion that is perpendicular to the plane of oscil-
lation at its endpoint.
a)
Fig. 6: Preventing elliptical motion (swing of the pendulum observed from above)
be carried out quickly and effectively, taking up just a few
minutes of the lesson.
Move the source of light for the situation in Fig. 5c until
the projection of the string stops moving on the screen
(Fig. 5b). By this means, the present plane of oscillation
can be accurately determined. A 36:1 vernier scale enab-
les the measurement of angles <1°.
b)

2.2 Technical data

Pendulum:
Suspension string:
Metal pendulum bob:
Protractor:
Protractro disc:
Divisions:
String projection by means of a light beam that can be
switched on and off
Incandescent lamp with lens: E10 3.7 V, 0.3 A
b)
8
c)
120 cm
38 mm Ø, 230 g
340 mm Ø, 360°
Vernier 0.1°
c)