Ocean 10, R. Lopez ����������������������������������������������������������������������� West
Valley College
Study Questions
11: Tides
1)
What
are tides?
2)
The
Earth and Moon spin together as a system in space, what is the name of the
center of mass for this Earth-Moon system?
3)
What
is gravitational force? The formula for gravitational force.
4)
The
Sun is 27 million times more massive than the moon, but the moon has a stronger
gravitational attraction the Earth�s oceans.�
Why (think of Newton�s gravitational formula)?
5)
Where
are gravitational forces strongest between the Earth and Moon?
6)
Where
are gravitational forces weakest between the Earth and Moon?
7)
What
is centrifugal force (inertia)?
8)
Are
centrifugal forces on all points on Earth equal in the Earth-Moon system?�
9)
Are
the centrifugal forces at different points parallel to each other or do they
point toward the center of mass of the moon like gravitational forces?
10)
Where
are centrifugal forces stronger than gravitational forces on Earth in the
Earth-Moon system?
11)
Where
are gravitational forces stronger than centrifugal forces on Earth in the
Earth-Moon system?
12)
Sketch the Earth-Moon system
below. Draw the gravitational forces and centrifugal forces at the points like
the nadar and zenith, north and south poles, the CE (just like in
lecture).� Make sure you draw the arrows
in lengths proportional to their strength (i.e., gravitational force arrows are
longer on the side closest to the moon).�
Also, label the barycenter. CE refers to the center of mass of Earth, CM
will be the center of mass of the moon.
13)
What
are tractive forces?� Label the tractive
forces on the figure above.
14)
On
the diagram in question 12 above, label the bulge that is the result of
gravitational forces and the bulge that is the result of the centrifugal
forces.
15)
Recall
that the bulges are the crests (high tides) of the tide waves and that the
areas between the crests (low tides) are the troughs of the tide waves.� In the equilibrium theory of tides, does the
Earth spin beneath these bulges or do the bulges move around the Earth?
16)
What
is a lunar tide?�
17)
Recall
that the Sun-Earth system also causes tide bulges due to the gravitational and
centrifugal forces associated with this system.� These work just like the Earth-Moon system but at only 46%.� What are solar tides?
18)
When
the Sun, Earth, and Moon are all in a line, the solar and lunar tides will be
additive, resulting in higher high tides and lower low tides.� What are these tides called?
19)
When
do the tides in the preceding question occur (i.e., what phase of the Moon)?
20)
When
the Sun, Earth, and Moon form a right angle, the solar tide will tend to
diminish the lunar tide.� What are these
tides called?�
21)
When
do they occur (i.e., what phase of the Moon)?
22)
What
are semidiurnal tides, diurnal tides, and mixed tides (know their patterns)?
23)
What
is the tide range?
24)
Why
do we get semidiurnal and mixed tides? In other words, as the Earth rotates
through the tidal bulges, what gets in the way of the rhythmic rise and fall of
the tides to cause these semidiurnal and mixed tides?
25)
What
are amphidromic points?
26)
In
the northern hemisphere, when a tide crest enters an ocean basin, why does the
tidal crest move in a counterclockwise motion when the Coriolis Effect must
cause everything else to rotate to the right?
27)
Why
does the rotation about the amphidromic point in the Pacific Ocean just west of
the North American coastline cause high tide to reach Santa Cruz half-hour
earlier than it reaches San Francisco?
28)
What
is a tidal bore?