center and the point of interest. Locations nearer the moon
experience a local gravitational force that is larger than
that experienced at locations farther away.
For the earth-moon system to remain in equilibrium,
the total centrifugal force must exactly balance the force
of gravitation attraction, or else the earth and moon
would accelerate away or toward each other. At the center
of the earth the two forces balance, but at locations nearer
to the moon the gravitation force is larger than the centrifugal force, and for locations farther away, the centrifugal
force is larger than the gravitational force (Figure 1a).
This difference is the tide-generating force (F t ), which
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Centifugal
Gravitational
Tide Generating
Tide Generating
Force
Centifugal
Force
Gravitational
Force
Tide Generating
Force
Centifugal
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Gravitational
Force
Tide Generating
Force
Centifugal
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Gravitational
Force
a
b
Tides, Figure 1 (a) The magnitude and direction of the tide-generating force on the earth (looking side on to the earth), created by
the balance between the centrifugal force and the gravitational force. (b) The horizontal component of the tide-generating force
which causes water movement.
TIDES
707