OCE1001 Chapter 9

The tides are considered an example of shallow-water waves because the tidal bulges have a wavelength that is on the order of a few centimeters a few meters tens of meters tens of kilometers thousands of kilometers

thousands of kilometers

If the side of Earth that faces the Moon experiences a tidal bulge (high tide), then the opposite side of Earth will experience a __________. tidal trough or low tide proxigean tide spring tide neap tide tidal bulge or high tide

tidal bulge or high tide

The low and high tides experienced on Earth are the result of __________. internal waves tidal bulges wind waves tsunami

tidal bulges

Resultant forces result in __________ tidal bulge(s) on Earth. three one four two

two

How many spring and neap tides occur each month? four spring tides and two neap tides four spring tides and four neap tides one spring tide and one neap tide two spring tides and four neap tides two spring tides and two neap tides

two spring tides and two neap tides

How many diurnal tides would you expect during one tidal period? one tide three tides two tides four tides

two tides

Why does the resultant tide-generating force create a tidal bulge on the side of Earth that faces away from the Moon? The centripetal force exceeds gravitational force at the zenith. The centripetal force is weaker than the gravitational force at the zenith. Centripetal force exceeds gravitational force at the nadir, or the point on Earth furthest from the Moon. The centripetal force is equal to the gravitational force at both the zenith and nadir. The centripetal force is weaker than the gravitational force at the nadir.

Centripetal force exceeds gravitational force at the nadir, or the point on Earth furthest from the Moon.

The image below shows the various positions of the Moon as it orbits Earth (north polar view). Correctly match the letters with the corresponding phases of the Moon.

D: Waxing gibbous (top left from Earth) B: Waxing crescent (top right from Earth) C: Waning crescent (bottom right from Earth) D: Waning gibbous (bottom left from Earth)

Where is/are Earth's tidal bulge(s) located? Choose all that apply. at the equator at the Tropic of Cancer at the zenith at the nadir at the Arctic Circle

- at the zenith - at the nadir

Which of the following statements about tides in a simple tidal bulge model is/are true? Choose all that apply. -A lunar or solar eclipse can occur only when the Moon is in syzygy. -Spring tides result from constructive interference between the solar and lunar tidal bulges. -Neap tides result from destructive interference between the solar and lunar tidal bulges. -Tides are greatest when the Moon is at apogee and Earth is at aphelion. -Wave interference does not affect tidal bulges. -Tides are greatest when the Moon is at perigee and Earth is at perihelion.

-A lunar or solar eclipse can occur only when the Moon is in syzygy. -Spring tides result from constructive interference between the solar and lunar tidal bulges. -Neap tides result from destructive interference between the solar and lunar tidal bulges. -Tides are greatest when the Moon is at perigee and Earth is at perihelion.

Of the following statements about tidal patterns and tidal charts, which is/are true? A semidiurnal tidal pattern has two low tides every tidal day. A mixed tidal pattern has two lows of unequal height and two highs of unequal height every tidal day. A diurnal tidal pattern has two high tides every tidal day. The tidal range is the difference in height between a high tide and a low tide. A tidal day is 24 hours and 50 minutes long. A mixed tidal pattern has two lows of about equal height and two highs of about equal height every tidal day.

-A mixed tidal pattern has two lows of unequal height and two highs of unequal height every tidal day. -The tidal range is the difference in height between a high tide and a low tide. -A semidiurnal tidal pattern has two low tides every tidal day. -A tidal day is 24 hours and 50 minutes long.

Disadvantages of tidal power plants relative to conventional thermal plants include higher initial plant costs, periodicity of tidal currents, and __________. high operating costs air pollution heat pollution excessive noise impacts on the marine environment

impacts on the marine environment

The weakest gravitational force caused by the Moon is called the __________, which is found at the point on Earth farthest from the Moon. tide-generating force zenith resultant force nadir barycenter

nadir

What do we call the tide that occurs when destructive interference between lunar and solar bulges produces a small tidal range? spring tide fall tide neap tide pean tide

neap tide

What do we call the tide that occurs when the constructive interference between the lunar and solar bulges produces a large tidal range? neap tide spring tide fall tide pean tide

spring tide

Some of the tide height numbers in your tide table are preceded by minus signs (or in some cases printed in red). This tells you that __________.

spring tides are occuring

A proxigean tide occurs when __________. the Moon is at apogee and its declination is zero the Moon is at quadrature and perigee at the same time there is a waxing gibbous Moon and the Sun is at aphelion the Moon is full and there is a neap tide the Moon is at perigee at a time of syzygy

the Moon is at perigee at a time of syzygy

What is the coastal tidal range? the height of sea level when high tide hits the shoreline the difference in maximum tide height between perigee and apogee the difference in sea level between a successive high and low tide the difference in maximum tide height between perihelion and aphelion the difference in maximum tide height between successive high tides

the difference in sea level between a successive high and low tide

What causes variation in Earth's tides over time? the orbits of the Moon around the Sun, and the Sun around Earth the elliptical orbit of Earth around the Sun and Moon the elliptical orbits of the Moon around Earth, and Earth around the Sun the elliptical orbit of the Moon around Earth the elliptical orbit of Earth around the Sun

the elliptical orbits of the Moon around Earth, and Earth around the Sun

Tidal forces result in two tidal bulges because __________. the gravitational attraction between Earth and the Moon is greater than the attraction between Earth and the Sun the centripetal force required to maintain the orbital relationship between the Moon and Earth is greater than the gravitational forces between them the velocity with which the Moon orbits Earth is greater than the velocity of Earth orbiting the Sun the supplied gravitational forces at various points within the planet differ from the centripetal force the materials of Earth are denser near the equator than near the poles

the supplied gravitational forces at various points within the planet differ from the centripetal force

Which of the following statements is/are true regarding Earth and the Moon? Choose all that apply. Earth rotates counterclockwise on its axis, or from west to east. There are two lunar tidal bulges and two solar tidal bulges. A new moon is one that you can't see because Earth is between the Moon and the Sun. The solar tidal bulges are larger than the lunar tidal bulges because the Sun is larger than the Moon. During a first quarter moon and a third quarter moon, the lunar and solar tidal bulges are additive.

-Earth rotates counterclockwise on its axis, or from west to east. -There are two lunar tidal bulges and two solar tidal bulges.

Of the following statements about the location of the barycenter of the Earth-Moon system, which is/are true? Choose all that apply. It is located in space between the Sun and the Earth-Moon system. It is located in space exactly halfway between Earth and the Moon. It is located at the center of mass of the Earth-Moon system. It is located at the exact center of Earth. It is located in space between Earth and the Moon, but it is closer to Earth. It is located at a point beneath Earth's surface within the mantle.

-It is located at the center of mass of the Earth-Moon system. -It is located at a point beneath Earth's surface within the mantle.

Which of the following statements is/are true regarding the lunar day and the solar day? Earth's rotation on its axis is why we experience day and night. One solar day is the time it takes for Earth to make one complete revolution around the Sun. It takes 50 minutes for a given location on Earth to "catch up" to the Moon. A lunar day is the time it takes for a location on Earth that is directly underneath the Moon to make one rotation and reach the same location directly underneath the Moon. The tides follow the solar day.

-It takes 50 minutes for a given location on Earth to "catch up" to the Moon. -A lunar day is the time it takes for a location on Earth that is directly underneath the Moon to make one rotation and reach the same location directly underneath the Moon. -Earth's rotation on its axis is why we experience day and night.

Which of the following statements is/are true regarding neap tides? Choose all that apply. Neap tides occur when there is a small tidal range. Low tides are low. High tides are low. Neap tides occur when solar tides and lunar tides are additive. Neap tides occur during first quarter moon and third quarter moon.

-Neap tides occur during first quarter moon and third quarter moon. -Neap tides occur when there is a small tidal range. -High tides are low.

Of the following statements about forces and tidal bulges, which is/are true? Choose all that apply. Hints On the side of Earth closest to the Moon, a tidal bulge will form as a result of an excess of centripetal force. On the side of Earth facing away from the Sun, a tidal bulge will form as a result of an excess of gravitational force. On the side of Earth closest to the Moon, a tidal bulge will form as a result of an excess of gravitational force. On the side of Earth facing away from the Sun, a tidal bulge will form due to an excess of centripetal force. Tidal bulges are produced only on the side of Earth closest to either the Moon or the Sun. Tidal bulges are produced on both sides of Earth from the Moon and the Sun.

-On the side of Earth closest to the Moon, a tidal bulge will form as a result of an excess of gravitational force. -On the side of Earth facing away from the Sun, a tidal bulge will form due to an excess of centripetal force. -Tidal bulges are produced on both sides of Earth from the Moon and the Sun.

Of the following statements about lunar phases, which is/are true? Choose all that apply. a. Over the few days of a waxing gibbous moon, the tidal range decreases. b. Over the few days of a waning gibbous moon, the tidal range increases. c. Over the few days of a waxing crescent moon, the tidal range increases. d. Over the few days of a waning crescent moon, the tidal range decreases. e. Over the few days of a waxing gibbous moon, the tidal range increases. f. Over the few days of a waxing crescent moon, the tidal range decreases.

-Over the few days of a waxing gibbous moon, the tidal range increases. -Over the few days of a waxing crescent moon, the tidal range decreases.

Which of the following statements is/are true concerning spring tides? Choose all that apply. Spring tides have high high tides. Spring tides occur when the Earth, Moon, and Sun are aligned. Spring tides occur only during the spring season. Spring tides have high low tides. Spring tides occur at first quarter moon and third quarter moon.

-Spring tides have high high tides. -Spring tides occur when the Earth, Moon, and Sun are aligned.

Of the following statements about the monthly tidal cycle, which is/are true? Choose all that apply. a. Spring tides occur twice a month. b. Neap tides occur twice a month. c. The full moon and the new moon affect the tides about the same. d. The new moon is associated with neap tide conditions. e. The full moon is associated with spring tide conditions. f. The new moon is associated with the smallest tidal range of the month.

-Spring tides occur twice a month. - Neap tides occur twice a month. - The full moon and the new moon affect the tides about the same. -The full moon is associated with spring tide conditions.

Of the following statements about the force of gravity between two bodies, which is/are true? Choose all that apply. The force of gravity between two bodies decreases as distance increases. The force of gravity between two bodies increases with an increase in mass. The force of gravity between two bodies decreases with an increase in mass. The force of gravity between two bodies is most affected by a change in mass. The force of gravity between two bodies is most affected by a change in distance. The force of gravity between two bodies increases as distance increases.

-The force of gravity between two bodies increases with an increase in mass. -The force of gravity between two bodies is most affected by a change in distance. -The force of gravity between two bodies decreases as distance increases.

Of the following statements about the contribution of the Sun and the Moon to Earth's tides, which is/are true? Choose all that apply. The Moon's contribution to the tides is less than that of the Sun. The lunar tidal bulges are about twice the size of the solar tidal bulges. The Sun exerts more than twice the gravitational pull of the Moon on Earth's tides because of its massive size. The solar tidal bulges are about twice the size of the lunar tidal bulges. The Sun's contribution to the tides is less than that of the Moon. The Moon exerts over twice the gravitational pull of the Sun on Earth's tides because of its proximity to Earth.

-The lunar tidal bulges are about twice the size of the solar tidal bulges. -The Sun's contribution to the tides is less than that of the Moon. -The Moon exerts over twice the gravitational pull of the Sun on Earth's tides because of its proximity to Earth.

Of the following statements about the tides, which is/are true? Choose all that apply. Hints There are two tidal bulges on Earth caused by the Moon: one facing the Moon, and the other facing away from the Moon. The Sun, because of its larger size, has more effect on Earth's tides than the Moon does. Although we observe the tides coming in and going out, in reality, Earth is rotating into and out of various tidal bulges, which produces changing tides. Both Earth and the Moon orbit around their common center of mass, called the barycenter. The tides are caused by an imbalance between the centripetal force and the gravitational force of the Moon and the Sun.

-There are two tidal bulges on Earth caused by the Moon: one facing the Moon, and the other facing away from the Moon. -Although we observe the tides coming in and going out, in reality, Earth is rotating into and out of various tidal bulges, which produces changing tides. -Both Earth and the Moon orbit around their common center of mass, called the barycenter. -The tides are caused by an imbalance between the centripetal force and the gravitational force of the Moon and the Sun.

Why is the length of a lunar day different from the length of a solar day? because the Moon revolves around Earth in the same direction that Earth is rotating on its axis because the Moon revolves around Earth in the opposite direction that Earth is rotating on its axis because the Moon is smaller than the Sun because Earth is larger than the Moon because the distance between Earth and the Moon is not constant

-because the Moon revolves around Earth in the same direction that Earth is rotating on its axis

Which phase(s) of the moon result in a low tidal range? Choose all that apply. full moon blue moon first quarter moon new moon third quarter moon

-third quarter moon -first quarter moon

In one solar day, how far does the Moon move around the Earth? 1/12th of a complete revolution 28 complete revolutions 1 complete revolution 1/28th of a complete revolution 1/6th of a complete revolution

1/28th of a complete revolution

If today high tide is at 1:00 p.m., what time will the same high tide be tomorrow? 1:50 p.m. 1:00 p.m. 12:35 p.m. 1:25 p.m. 12:10 p.m.

1:50pm

It is Thursday and an angler is planning a fishing trip in two days on Saturday. The angler knows from experience that the fishing is best at a particular location at the beginning of high tide. He does not have a tide table, but the angler noted that the high tide on Thursday was at 12:15 PM. At what time on Saturday should he plan to arrive to start fishing, assuming that this location has a diurnal tide type? 1:55 PM 2:45 PM 1:05 PM 12:15 PM 12:15 AM

1:55pm

How many spring and neap tides will a tide-recording station experience in a given month? 1 to 3 spring tides and 3 to 4 neap tides 3 to 4 spring tides and 1 to 3 neap tides 2 spring tides and 2 neap tides 1 spring tide and 1 neap tide

2 spring tides and 2 neap tides

A lunar day is __________ in duration. 48 hours 24 hours and 50 minutes 24 hours 12 hours 12 hours and 25 minutes

24 hours and 50 minutes

What is the length of a lunar day? 24 hours 28 days 12 hours 14 days 24 hours and 50 minutes

24 hours and 50 minutes

It is Wednesday, and you are planning a fishing trip for this coming Saturday. You have heard that fishing is best at your chosen spot when the ebb current begins to flow, so you wish to start fishing at high tide. You do not have a tide table, but you have noted that today's high tide was at 1:10 p.m. At what time on Saturday should you plan to arrive and start fishing?

3:40pm

In an amphidromic cell with a normal tidal cycle, what cotidal line would experience high tide if low tide were occurring along cotidal line 2? 4 6 8 0 10

8

In the figure above, which shows a hypothetical tidal pattern over a 24-hour period. Which letter(s) represent(s) high tide? Choose all that apply. A B C D E

A,C,E

This image depicts the orbital relationships of the Sun, the Moon, and Earth. Match the correct letters to the following positions of the Moon and Earth.

A: Apogee (left of Earth) D: Aphelion (left of sun) B: Perihelion (right of sun) C: Perigee (right of Earth)

Why does the Moon generate larger tidal forces than the Sun? Although the Moon is bigger, the Sun is much closer. Although the Moon is further away, the Sun is much smaller. Although the Sun is bigger, the Moon is much closer. Although the Sun is further away, the Moon is much smaller.

Although the Sun is bigger, the Moon is much closer.

The diagram below shows the position of the Earth-Moon-Sun system during neap tide conditions. Match the correct letters to the following items.

C: Lunar tidal bulges (bottom of Earth) D: First-quarter moon (above Earth) B: Third- or last-quarter moon (below Earth) A: Solar tidal bulges (top of Earth)

If you had to navigate a ship into a shallow, rocky harbor with mixed tides, when would be the best time for you to do it? Approaching the low slack water During the maximum flood current Approaching the high slack water During the transition from ebb to flood current During the maximum ebb current

Approaching the high slack water

In the figure above, assume black arrow (1) is the gravitational force and black arrow (2) is the centripetal force on the surface of a hypothetical planet. Which of the red arrows would represent the resultant force? A B C D E

B

On the image below, match the letter to the correct tidal pattern or tide chart feature.

B: Area with semidiurnal tidal pattern (arrow pointing right from Africa) C: Area with mixed tidal pattern (arrow pointing down/right from South America) E: Tidal range (middle chart) D: Datum (bottom chart) F: Tidal period (top chart) A: Area with diurnal tidal pattern (arrow pointing up/right from USA)

The diagram below shows the position of the Earth-Moon-Sun system during spring tide conditions. Match the correct letters to the following items.

B: New moon (closest to sun) A: Solar tidal bulge (top Earth) D: Full Moon (furthest from sun) C: Lunar tidal bulge (bottom Earth)

What is Newton's Law of Universal Gravitation? a. F = Gm1m2/r2 b. F = ma c. F = m1m2/r d. F = m1m2/r2 e. P = mv

F = Gm1m2/r2

Why are the idealized high tides at the equator all about the same height? Locations at the equator pass through the same part of the two tidal bulges with each high tide. Water at the equator cannot move as fast because it is hot. The equator does not pass through the tidal bulges. Locations at the equator pass through different parts of the two tidal bulges with each high tide. The equator goes all the way around Earth.

Locations at the equator pass through the same part of the two tidal bulges with each high tide.

What path did the rotating item take at the moment when the string was let go? Its path did not change; it continued in a nearly circular orbit. It flung off and hit the globe. It went behind him and hit the vase of flowers. It traveled in a straight-line path that was tangent to its circular orbit. It flew off directly toward the camera.

It traveled in a straight-line path that was tangent to its circular orbit.

Which factor would increase the amount of energy an estuarine tidal power plant could generate? a. Large estuarine volume b. Broad connection to sea c. Small tidal range d. Diurnal tidal pattern e. Weak ebb and flood currents

Large estuarine volume

What tidal pattern would best describe a coastline that experienced a maximum tidal range of 6 feet in the morning and a smaller 2-foot range in the late afternoon? Diurnal Neap Mixed Semidiurnal Spring

Mixed

The most important factor that causes ocean tides on Earth is the __________. Moon Sun Coriolis effect Earth's rotation configuration and depth of the ocean basins

Moon

What is the difference between perihelion and aphelion? Perihelion is when Earth is farthest from the Sun, and aphelion is when it is closest to the Sun. Perihelion is when Earth is closest to the Sun, and aphelion is when it is farthest from the Moon. Perihelion is when the Moon is closest to the Sun, and aphelion is when it is farthest from the Sun. Perihelion is when Earth is closest to the Sun, and aphelion is when it is farthest from the Sun. Perihelion is when Earth is closest to the Moon, and aphelion is when it is farthest from the Moon.

Perihelion is when Earth is closest to the Sun, and aphelion is when it is farthest from the Sun.

Why is the idealized highest high tide at 28 degrees south latitude delayed by 12 hours from the highest high tide at 28 degrees north latitude? That is how long it takes for the location at 28 degrees south latitude to make one complete rotation. That is how long it takes for the location at 28 degrees south latitude to rotate into the tail end of the high tide bulge. That is how long it takes for the location at 28 degrees south latitude to rotate into the largest part of the high tide bulge. Twelve hours is half of a day, so it takes 12 hours for the tides to catch up. The locations are at different latitudes, so they experience different idealized tidal patterns.

That is how long it takes for the location at 28 degrees south latitude to rotate into the largest part of the high tide bulge.

If it is January and the Moon is in syzygy, which additional factor would contribute to extreme tidal ranges around the world? a. The Moon in quadrature b. The Moon in perigee c. The Earth in aphelion d. The Moon in apogee

The Moon in perigee

Why does the Moon reach perigee two days before it completes its 29-and-a-half-day lunar cycle? Earth's orbit around the Moon is elliptical. The Moon's orbit around Earth is elliptical. The Sun's orbit around Earth changes the position of the Moon's elliptical orbit. Earth's orbit around the Sun shifts position over time. The Moon's orbit around Earth shifts position over time.

The Moon's orbit around Earth shifts position over time.

Where on Earth is the centripetal force toward the Moon the greatest? at the South Pole The centripetal force is the same everywhere on Earth. at the zenith at the North Pole at the nadir

The centripetal force is the same everywhere on Earth.

what are tides? -the regular daily rises and falls in sea level caused by the gravitational attraction of the Moon on Earth -the regular daily rises and falls in sea level caused by the gravitational attraction of the Moon and Sun on Earth -the regular daily rises and falls in sea level caused by the gravitational attraction of the Sun on Earth -the regular weekly rises and falls in sea level caused by the gravitational attraction of the Moon on Earth -the regular weekly rises and falls in sea level caused by the gravitational attraction of the Moon and Sun on Earth

The regular daily rises and falls in sea level cased by the gravitational attraction of the Moon and Sun on Earth

How is a semidiurnal period related to a tidal day? The semidiurnal period is not related to a tidal day. The semidiurnal period is half as long as a tidal day. The semidiurnal period is twice as long as a tidal day. The semidiurnal period is about as long as a tidal day.

The semidiurnal period is half as long as a tidal day.

At 28 degrees north latitude, why are some idealized high tides higher and some high tides lower? There is more interference from land during the lower high tides. The tidal bulges are rarely centered on the equator, so this location passes through different parts of the two tidal bulges. There are magnetic anomalies here that counteract the lower high tide. The tidal bulge directly beneath the Moon is smaller than the tidal bulge directly opposite the Moon. The climate here is variable.

The tidal bulges are rarely centered on the equator, so this location passes through different parts of the two tidal bulges.

Why are high tides found simultaneously on opposite sides of Earth? The tidal bulges occur on both sides of Earth that are perpendicular to the tide-generating body. The ocean water experiencing low tide rotates around Earth on a 12-hour cycle. The ocean water experiencing high tide rotates around Earth on a 12-hour cycle. The tidal bulges occur on both sides of Earth that are aligned with the tide-generating body.

The tidal bulges occur on both sides of Earth that are aligned with the tide-generating body.

As illustrated on the left side of the SmartFigure tide graph, why is the idealized high tide at 28 degrees north latitude higher than the corresponding high tide at 28 degrees south latitude? These two locations are passing through different parts of the same tidal bulge at the same time. While the location at 28 degrees north latitude is experiencing a high tide, the location at 28 degrees south latitude is experiencing a low tide. There are fewer landmasses in the Southern Hemisphere. There is less water in the Southern Hemisphere. Landmasses get in the way of the tides in the Southern Hemisphere.

These two locations are passing through different parts of the same tidal bulge at the same time.

What do we call the time that passes between two high tides? tidal datum tidal range tidal day tidal period

Tidal period

A grunion "run" would be expected within a few nights after __________. a. a fully developed sea b. a quarter moon c. a new or full moon d. the autumnal equinox e. a period of heavy surf

a new or full moon

What common household item is used in this video to demonstrate the forces that act on bodies to create tides on Earth? a can of soda a racquetball a balloon a light bulb an apple

a racquetball

A relatively small tidal range could be expected

at an amphidromic point.

Where on Earth is the gravitational attraction toward the Moon the greatest? at the South Pole The gravitational attraction is the same everywhere on Earth. at the zenith at the North Pole at the nadir

at the zenith

Tides occur on Earth because of an imbalance between gravity and __________. friction the Coriolis effect dark energy centripetal force centrifugal force

centripetal force

What are Earth's three different tidal patterns called? diurnal, semidiurnal, and mixed tidal, semitidal, and mixed tidal, semitidal, and moderate diurnal, semidiurnal, and moderate

diurnal, semidiurnal, and mixed

A boat is most likely to be carried out to sea from a harbor by a(n) __________.

ebb current

On the side of Earth closest to the Moon, gravitational forces __________ the centripetal forces. are less than exceed equal

exceed

How many semidiurnal tides would you expect during one tidal period? three tides four tides one tide two tides

four tides

What pattern of tides would you expect to see for a mixed tidal system? four tides of different heights two tides of different heights two tides of roughly equal heights four tides of roughly equal heights

four tides of different heights

The Moon's influence on Earth's tides is __________ the influence of the Sun. less than greater than the same as

greater than

A centrifugal force is one that is directed _____ and a centripetal force is one that is directed _____. outward; inward inward; outward outward; outward inward; inward

outward; inward

You have just arrived for a vacation on the Oregon coast, and you wish to explore some tide pools while you are there. You hear the local weatherman say that there will be a minus tide at 7 a.m. tomorrow. You should __________. -Wait for a minus tide that occurs at night, because there is not much to see in tide pools in the daytime -not worry about it, because tidepooling is good every day at low tide -sleep in; you know that Oregon has a mixed tide pattern and that there will be another low tide in about 12-1/2 hours -set your alarm to wake you early; this may be your best chance for tidepooling -Wait two weeks until the end of your vacation, because the tidal range will be lower then

set your alarm to wake you early; this may be your best chance for tidepooling

When would the oceans experience the greatest tidal range? when Earth is in perigee and the Moon is in perihelion when Earth is in apogee and the Moon is in perigee when Earth is in aphelion and the Moon is in perigee when Earth is in perihelion and the Moon is in perigee when Earth is in aphelion and the Moon is in apogee

when Earth is in perihelion and the Moon is in perigee

The gravitational force exerted on Earth by the Moon is greatest at the _________________. poles zenith nadir barycenter equator

zenith