Deck 10: Gravity Is More Than Keplers Laws

Question 1

Chaos means that although one can describe the motion of three or more bodies due to their gravitational interactions with each other,it is not possible to predict their motion exactly over long periods of time.

Answer 1

True

Question 2

If high tide occurred at .today,when will high tide occur tomorrow afternoon?

A) 12:00 noon
B) 11:00 A.M.
C) 11:30 A.M.
D) 12:30 P.M.

Answer 2

12:30 P.M.

Question 3

Tides are strongest when the Moon is at first quarter phase or third quarter phase.

Answer 3

False

Question 4

The force of gravity at the center of Earth,compared to its surface gravity,is equal to

A) .
B) .
C) .
D) zero.

Question 5

If you arrive at the beach and see that the Moon is 45 degrees above the western horizon,you know that

A) high tide will occur in about six hours.
B) low tide will occur in about six hours.
C) low tide occurred three hours ago.
D) high tide occurred three hours ago.

Question 6

The Moon's tidal forces on Earth result in it pulling the near side of Earth toward it and pushing the far side of Earth away from it.

Question 7

Roughly how often does a high tide occur?

A) Once every 6 hours
B) Once every 12 hours
C) Once every 18 hours
D) Once every 24 hours

Question 8

If a moon wanders closer than approximately 5 times the radius of a planet,the moon will likely be torn apart by tidal forces.

Question 9

Tides cause the poles of Earth to be pulled closer to each other than they would otherwise be.

Question 10

If you were standing inside the Earth at a radius where half the Earth's mass was above you and half the Earth's mass was below you,the gravitational pull of the Earth would be one half of that on its surface.

Question 11

No matter what shape Earth might be,the combined force of gravity from all the pieces of Earth would still pull on you perpendicular to the surface on which you are standing.

Question 12

Ocean tides on Earth are caused only by the Moon.

Question 13

Although the Sun's gravitational pull on Earth is nearly 200 times greater than the Moon's,its tidal effect is only about 50 percent of the Moon's tidal effect.

Question 14

Because of conservation of angular momentum,as the Earth's rotation slows in response to the Moon's tidal pull,the Moon's distance from Earth increases.

Question 15

The fact that the Earth is elastic and responds to the Moon's tidal stress by bulging causes the Earth's rotation speed to gradually increase over time.

Question 16

The tidal stress on a moon as it orbits a planet can heat the moon's core hot and keep it from solidifying.

Question 17

Because of libration,we can see over 50 percent of the Moon's surface from Earth.

Question 18

Orbital resonances produce gaps in Saturn's rings.

Question 19

A planet could not form in the asteroid belt because at this radius there is an orbital resonance with the Sun and Saturn.

Question 20

High tides occur twice every 25 hours.

Question 21

If a moon is asymmetric,but it has a circular orbit around a planet,over time

A) its orbit will become more elliptical.
B) its orbit will decay and the moon eventually will be torn apart.
C) its rotation rate will become equal to its orbital period.
D) its rotation rate will increase.

Question 22

Consider a person of mass m trapped inside a hollow sphere of mass M and radius R.What is the force of gravity on the person if he/she stands at a radius of 0.5 R?

A)
B)
C)
D) 0

Question 23

How has the Moon affected Earth's axial tilt?

A) It is because of the Moon that Earth's axis is tilted relative to its orbital plane.
B) It is because of the Moon that Earth's axial tilt is relatively steady.
C) It is because of the Moon that Earth's axial tilt is slowly increasing over time.
D) It is because of the Moon that Earth's axial tilt varies chaotically over large time scales.

Question 24

If the Moon were twice as far away from Earth as it is now,the strength of its tidal forces would be

A) the same.
B) half as strong.
C) one-fourth as strong.
D) one-eighth as strong.

Question 25

What are the fewest high tides it is possible to have in one day?

A) Zero
B) One
C) Two
D) Three

Question 26

How does the tidal force of Jupiter on its moon Europa compare to that of the Earth on the Moon? Europa has a semimajor axis that is 1.7 times the Moon's semimajor axis,and a mass that is 0.7 times that of the Moon.The diameter of Jupiter is 11 times that of the Earth,and the mass of Jupiter is 320 times that of the Earth.

A) The tidal force on Europa due to Jupiter is 500 times the tidal force on the Moon due to Earth.
B) The tidal force on Europa due to Jupiter is 2,400 times the tidal force on the Moon due to Earth.
C) The tidal force on Europa due to Jupiter is 4,000 times the tidal force on the Moon due to Earth.
D) The tidal force on Europa due to Jupiter is 7 times the tidal force on the Moon due to Earth.

Question 27

In the past,the Moon was closer to the Earth and the difference in the heights of the ocean at high and low tides were

A) the same.
B) larger.
C) smaller.
D) Tides were nonexistent in the past.

Question 28

When the Earth's rotation slows because of tidal effects due to the Moon,in order to conserve orbital angular momentum,

A) the Moon's distance will increase.
B) the Moon's distance will decrease.
C) the Moon's orbital speed will decrease.
D) the Moon's rotation rate will increase.

Question 29

How do the Sun's and Moon's tidal forces on Earth compare?

A) Because it is more massive,the Sun exerts more tidal force on Earth than the Moon does.
B) Because it is closer,the Moon exerts more tidal force on Earth than the Sun does.
C) The Sun and Moon exert equal tidal forces on Earth.
D) Only the Moon's tidal force is significant because the Sun is too far away to have any real effect.
E) Only the Sun's tidal force is significant because the Moon is not massive enough to have any real effect.

Question 30

Ocean beach tides are higher than land tides because

A) tides affect solid earth more than liquid water.
B) water can flow,but land cannot.
C) tides affect liquid water more than solid earth.
D) tides affect liquid and solid equally.

Question 31

As Earth's rotation slows over time,Earth loses angular momentum.What happens to it?

A) It is transferred to the Moon,which causes the Moon to rotate faster.
B) It is transferred to the Moon,which causes the Moon to increase its orbital radius.
C) It is transferred to the Moon,which causes the Moon to increase its orbital period.
D) Angular momentum is not conserved in this case.

Question 32

The rotation of the Moon is tidally locked to its orbital motion around Earth because

A) the Moon's orbit is elliptical.
B) Earth's orbit around the Sun is elliptical.
C) the Sun is far more massive than the Moon.
D) Earth is far more massive than the Moon.

Question 33

Io's volcanic activity is due to tidal forces exerted by

A) Saturn.
B) Jupiter.
C) the Sun.
D) a moon named Europa.

Question 34

Neap tide occurs when the Moon is in the first or third quarter phase and results in

A) smaller than usual tides.
B) larger than usual tides.
C) No tides.

Question 35

Consider a particle inside the Earth located a distance of one-third the Earth's radius from the center of the Earth.Assuming the Earth has a uniform density,how would the gravitational force on that particle compare to the gravitational force it would experience at the Earth's surface?

A) The gravitational force at one-third would be 3 times smaller than at the Earth's surface.
B) The gravitational force at one-third would be 3 times larger than at the Earth's surface.
C) The gravitational force at one-third would be 9 times smaller than at the Earth's surface.
D) The gravitational force at one-third would be 9 times larger than at the Earth's surface.

Question 36

How does the size of the tidal force on the Earth due to the Moon compare with the tidal force on the Moon due to the Earth? Recall that the Earth's diameter is approximately 4 times that of the Moon,and Earth's mass is approximately 80 times that of the Moon.

A) They are exactly the same.
B) The tidal force on the Earth is 4 times that on the Moon.
C) The tidal force on the Moon is 20 times that on the Earth.
D) The tidal force on the Moon is 4 times that on the Earth.

Question 37

Based on the length of a lunar cycle,if there is a spring tide today,how long will it be until the next spring tide?

A) About three to four days
B) One week
C) Two weeks
D) One month

Question 38

How much of the Moon's surface can we see from Earth?

A) 40 percent
B) 50 percent
C) 60 percent
D) 100 percent

Question 39

Due to tidal bulging of Earth and the Moon and the gravitational attraction between them,all of the following are true,EXCEPT

A) The Moon is moving away from Earth.
B) The Moon's orbit is becoming more circular.
C) Lunar cycles are slowly getting longer.
D) Solar and lunar eclipses are becoming more common.

Question 40

Consider the tidal force at the Earth's North Pole due to the Moon.The tidal force is pointed directly

A) toward the Moon.
B) toward the center of the Earth.
C) away from the center of the Earth.
D) away from the Moon.

Question 41

Which of the following orbital periods for asteroids would NOT be associated with one of the Kirkwood gaps given that Jupiter's orbital period is 11.9 years?

A) 5.95 years
B) 4.76 years
C) 3.97 years
D) 3.72 years

Question 42

How does the tidal stress on the Earth's oceans due to the Moon vary with latitude on the Earth? Consider four points on the Earth: (1)on the equator on the side closest the Moon, (2)on the equator on the side farthest from the Moon, (3)at the North Pole,and (4)at the South Pole.Draw a diagram and show the direction of the tidal stress at each point.

Question 43

The Trojan asteroids are classified as a distinct group of asteroids because they are found

A) at two Lagrangian points in the Jupiter/Sun system.
B) in one of the Kirkwood gaps.
C) in the Cassini Division around Saturn.
D) at the Lagrangian point between Earth and the Sun.

Question 44

What causes the tides on Earth,and how frequently do high and low tides occur?

Question 45

In a three body system,gravity controls the motion of each of the objects,

A) and their future positions can be predicted accurately at any time in the future.
B) and their future positions can be predicted accurately at any time in the past.
C) but we cannot predict their positions far into the future because of friction.
D) but we cannot accurately predict their positions far into the future due to chaos.

Question 46

Comet Shoemaker-Levy 9 split into many pieces before crashing into Jupiter because

A) the comet collided with a moon of Jupiter.
B) the comet came within the Roche limit of Jupiter.
C) the comet melted as it absorbed sunlight.
D) the comet crossed an Lagrangian equilibrium point.

Question 47

Explain why a person at the center of Earth would be weightless.

Question 48

Neptune's radius is 25,000 km.Which of the following would we be UNLIKELY to see orbiting Neptune?

A) A ring with a semimajor axis of 90,000 km
B) A ring with a semimajor axis of 50,000 km
C) A moon with a semimajor axis of 120,000 km
D) A moon with a semimajor axis of 70,000 km
E) A ring at any radius

Question 49

If the mass of the Sun is roughly 30,000,000 times greater than the mass of the Moon,and its distance is roughly 400 times farther,estimate the strength of the Sun's tidal forces compared to the Moon's tidal forces.

Question 50

The moons of Saturn named Tethys and Dione have a 2:3 orbital resonance with Tethys orbiting closer to Saturn than Dione.If the semimajor axis of Dione's orbit is 380,000 km,what is the semimajor axis of Tethy's orbit?

A) 700,000 km
B) 570,000 km
C) 290,000 km
D) 250,000 km

Question 51

Saturn's ring system has a very sharp outer edge because

A) particles at the edge have a 7:6 orbital resonance with a pair of co-orbiting moons that lie just outside the rings.
B) the edge marks the Roche limit.
C) of a pair of shepherding moons.
D) Saturn has a thicker atmosphere than Earth.

Question 52

Tides play a role in the interaction between which types of systems?

A) Tides play a role in all of these systems.
B) Two stars orbiting around each other
C) Objects moving close to a black hole
D) Two galaxies passing close to each other

Question 53

The SOHO satellite is located in

A) a stable orbit at the Lagrangian point in the Earth/Sun system.
B) a stable orbit at the Lagrangian point in the Earth/Sun system.
C) a polar orbit around the Earth.
D) an equatorial orbit around the Sun.

Question 54

When the Moon was half its present distance to the Earth,how much larger was its tidal force on the Earth's oceans?

Question 55

The Cassini Division in Saturn's rings is caused by an orbital resonance with its moon named

A) Titan.
B) Mimas.
C) Triton.
D) Dione.

Question 56

When a tiny change in a system's parameters.such as position or speed,can develop into large differences in later motion or behavior,the system is called

A) unpredictable.
B) chaotic.
C) quantum mechanical.
D) deterministic.

Question 57

Assume for a moment that Earth has a uniform density throughout its interior.Given this,how would the force of gravity felt at an interior distance of half an Earth radius compare to the surface force of gravity?

Question 58

Why is the space station not torn apart by tides from Earth?

A) It is too close to the center of Earth.
B) It lies outside the Earth's Roche limit.
C) It is held together by nuts and bolts.
D) Its self-gravity is too strong.

Question 59

Why does Saturn have rings while Earth does not?

A) Saturn is cooler than Earth.
B) Saturn is more massive than Earth.
C) Saturn rotates faster than Earth.
D) Saturn has a thicker atmosphere than Earth.

Question 60

Gaps in Saturn's rings are caused by

A) shepherd moons.
B) orbital resonances.
C) moons that collide with material and clear out their orbit.
D) All of the above

Question 61

Jupiter's tidal force on its moon Europa is thought to keep Europa's interior hot enough for liquid oceans to exist under its icy surface.How much larger is the tidal force of Jupiter on Europa compared to that of the Earth on the Moon? Europa has a semimajor axis that is 1.7 times the Moon's semimajor axis,and a mass that is 0.7 times that of the Moon.The diameter of Jupiter is 11 times that of the Earth,and the mass of Jupiter is 320 times that of the Earth.

Question 62

Explain why few asteroids are found within the Kirkwood gaps in the asteroid belt.

Question 63

How many Lagrange equilibrium points are there around a planet that orbits the Sun,approximately where are they located (draw a diagram),and why are they important?

Question 64

The Cassini Division in the rings of Saturn occurs because particles that would orbit in the gap would have a 2:1 orbital resonance with Mimas,one of Saturn's moons.If Mimas' orbital period is 0.94 days and its semimajor axis is 186,000 km,then what is the semimajor axis of the Cassini Division?

Question 65

If we characterize a chaotic system as being "deterministic but unpredictable," what do we
mean?

Question 66

What is the Roche limit and how large is it for a planet of radius R?

Question 67

How would Earth's shape change if there were no Moon?

Question 68

Explain how the Moon became tidally locked with Earth.

Question 69

Because the Earth rotates in the same direction as the Moon orbits it,the added gravitational pull of Earth's tidal bulge causes the Moon's orbital speed to increase over time.The opposite happens for Neptune's moon Triton,which orbits in a direction opposite to Neptune's rotation.Because of its change in orbital speed,what will happen to Triton's orbital distance over time?