ausblenden:
Schlagwörter:
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Zusammenfassung:
In a coordinate system fixed with respect to the rotating
Earth, the Coriolis force deflects an object sideways relative
to its direction of motion. A beautiful demonstration
of that effect is the Foucault pendulum, illustrated in
figure 1a. As the long pendulum rocks back and forth, the
Coriolis force deflects it the same way on both the forward
and reverse swings—to the right in the Northern Hemisphere
and to the left in the Southern Hemisphere. The net result is
that the pendulum’s plane of oscillation rotates clockwise in the
Northern Hemisphere, a change evidenced in figure 1a by the
little cylinders that the pendulum has knocked down.
The time rate of change of the oscillation direction is given
by ϕ˙ = −Ω cosθ, where, as illustrated in figure 1b, Ω is the rotation
rate of Earth and θ is the colatitude—that is, the angle
between the local vertical and Earth’s rotation axis. The minus
sign arises because the pendulum maintains its oscillation direction
as Earth rotates under it. As a consequence, the pendulum’s
direction of oscillation rotates in the sense opposite that
of Earth’s rotation, a result most readily visualized by imagining
the pendulum to be at the North Pole.
