Deck 4: Gravitation and the Waltz of the Planets

Question 1

Why do you think the planets were chosen as key indicators of a person's destiny by early astrologers?

A)They stayed in the same places with respect to the stars but were very bright.
B)They moved in complicated (but predictable) patterns with respect to the stars.
C)They twinkled and their colors varied randomly.
D)They moved very uniformly across the sky, night by night.

Answer 1

B

Question 2

The Ptolemaic model of the universe included each of the following features, except one. Which one is the exception?

A)The Sun and the Moon revolve around Earth.
B)The planets move in circular orbits called epicycles. The centers of the epicycles move along circular orbits called deferents.
C)Comets are within Earth's atmosphere.
D)The apparent daily motion of the stars is due to the rotation of Earth.

Answer 2

D

Question 3

Greek philosophy after about 600 B.C.E., beginning with the Pythagoreans and others, was quite different from the philosophies (Babylonian, Egyptian, etc.) that preceded it. What was this important difference?

A)The Greeks adopted a Sun-centered model of the universe and rejected the earlier Earth-centered model.
B)The Greeks rejected mythological explanations for the cosmos and sought natural causes.
C)The Greeks adapted elliptical orbits for the planets and rejected the earlier circular orbits.
D)The discovery of parallax measurements gave the Greeks, for the first time, a sense of the true size of the universe.

Answer 3

B

Question 4

If Mars is moving retrograde it will rise above which horizon?

A)north
B)south
C)east
D)west

Question 5

In Ptolemy's geocentric theory of the solar system, what name is given to the large circle centered on Earth through which the center of a smaller circle moves as the planet moves around the smaller circle?

A)ecliptic
B)deferent
C)celestial equator
D)epicycle

Question 6

According to the Greek geocentric model, Earth's rate of rotation on its axis is:

A)zero.
B)once in 24 hours.
C)once per month.
D)once per year.

Question 7

In the geocentric Ptolemaic model that described the apparent motions of planets against the background sky as viewed from a stationary Earth, at what distance with respect to its deferent is a particular planet on its epicycle when it appears to stop moving for a short period in its motion against the background?

A)at a distance greater than the radius of the deferent
B)anywhere around the epicycle
C)at a distance well inside the deferent
D)close to the deferent

Question 8

One unsatisfactory feature of the Ptolemaic description of the planetary system, particularly from a philosophical point of view, was:

A)that it needed continuous updating of the parameters of epicycle and deferent sizes and speeds to match planetary motions over time periods of more than one or two decades.
B)the fact that, although it described planetary motions in general, it could not be used for prediction of future planetary positions.
C)the requirement of many unrelated parameters, such as epicycle and deferent sizes and speeds, with no unifying rules.
D)the fact that it placed Earth at the center of the system, whereas Greek philosophers were convinced that the Sun was at the center.

Question 9

The occasional retrograde motion of Mars against the background stars is the result of the:

A)observation of a moving Mars from Earth, whose orbital motion is faster than that of Mars.
B)observation of a rapidly moving Mars from a more slowly moving Earth.
C)variable speed of Mars because its orbit is elliptical.
D)observation of Mars from the rapidly rotating Earth.

Question 10

In the path of Mars against the background stars shown in Figure 4-2 of Universe, 11th ed., the planet appears from Earth to move in a loop, moving westward for a period of time. What is the approximate angle between the Earth-Sun line and the Earth-Mars line when the planet is halfway through the westward, or retrograde, motion on about June 1?
​
​

A)180°
B)It can be any angle.
C)0°
D)90°

Question 11

The geocentric model for the solar system became unsatisfactory to astronomers compared with the heliocentric model early in the sixteenth century. Each of the following is part of the explanation for this except one. Which is the exception?

A)Isaac Newton was able to derive all planetary motion from one universal law of gravity.
B)The heliocentric model was conceptually simpler.
C)The invention of the telescope provided observations that were in better agreement with a heliocentric model.
D)Observations by spacecraft proved that all planets orbited the Sun.

Question 12

Which one of the following statements about the observation of retrograde motion is correct? Retrograde motion can be observed on:

A)the Sun, for all the planets.
B)Mars, just for the inner planets.
C)Earth, just for the outer planets.
D)Jupiter, for all the planets.

Question 13

Copernicus's model for the planetary system:

A)retained Earth at the center of the solar system but eliminated epicycles.
B)placed the Sun at the center of the solar system and eliminated epicycles completely.
C)placed the Sun at the center of the solar system but retained the idea of epicycles.
D)had Earth at the center of the solar system and the planets moving in epicycles.

Question 14

Copernicus's nationality was:

A)Greek.
B)Italian.
C)Egyptian.
D)Polish.

Question 15

Which of the following planets passes between Earth and the Sun?

A)Neptune
B)Mars
C)Jupiter
D)Venus

Question 16

At what position in its orbit will an inferior planet appear to be moving, for a day or two, more or less directly toward Earth? (See Figure 4-6 of Universe, 11th ed., and draw a diagram if it will help.)
​
​

A)greatest western elongation
B)inferior conjunction
C)superior conjunction
D)greatest eastern elongation

Question 17

At which configuration is a planet whose angle of elongation is 0°?

A)conjunction
B)retrograde
C)opposition
D)It is not possible for a planet to have an elongation of 0°.

Question 18

When observed at greatest eastern elongation (see Figure 4-6 of Universe, 11th ed.), Venus is about 45° from the Sun. How long after sunset does Venus set on the western horizon?
​
​

A)about 3 hours
B)It does not set at this specific time in its orbit.
C)1 hour
D)about 10 minutes

Question 19

Greatest elongation in a planetary orbit occurs when the angle between:

A)Sun-planet and Earth-planet lines is 90°.
B)Earth-planet and Sun-planet lines is at maximum.
C)Sun-Earth and planet-Earth lines is 90°.
D)Sun-Earth and Sun-planet lines is 90°.

Question 20

A superior planet is closest to Earth when it is near:

A)the vernal equinox.
B)opposition.
C)conjunction.
D)maximum eastern elongation.

Question 21

A superior planet is farthest from Earth when it is near:

A)the vernal equinox.
B)opposition.
C)maximum eastern elongation.
D)conjunction.

Question 22

The synodic period of a planet is the time between:

A)successive alignments of the Sun, the planet, and Earth (e.g., time between successive oppositions).
B)successive alignments of the Sun, the planet, and a particular point on the sky (e.g., a star).
C)its passage from conjunction to opposition in its orbit.
D)successive passages of the planet across the celestial equator.

Question 23

How many times is Mars at inferior conjunction during one orbit around the Sun?

A)zero
B)one
C)two
D)three

Question 24

How does Jupiter's sidereal period compare with its synodic period?

A)Because Jupiter rotates rapidly on its axis, its sidereal period is longer than its synodic period.
B)Because Jupiter rotates rapidly on its axis, its synodic period is longer than its sidereal period.
C)Because Jupiter is one of the outer planets, its sidereal period is longer than its synodic period.
D)Because Jupiter is one of the outer planets, its synodic period is longer than its sidereal period.

Question 25

The sidereal period of Jupiter is almost 12 years. Its synodic period is:

A)longer than this.
B)about one-half of this.
C)slightly longer than 1 year.
D)slightly shorter than 1 year.

Question 26

The synodic periods of the following outer planets, from shortest to longest, are:

A)Jupiter, Saturn, and Uranus.
B)Uranus, Saturn, and Jupiter.
C)Saturn, Uranus, and Jupiter.
D)There is no simple relationship among the synodic periods of these planets.

Question 27

The sidereal periods of the following outer planets, from shortest to longest, are:

A)Jupiter, Saturn, and Uranus.
B)Uranus, Saturn, and Jupiter.
C)Saturn, Uranus, and Jupiter.
D)There is no simple relationship among the sidereal periods of these planets.

Question 28

The synodic period of a superior planet in motion around the Sun, as viewed from Earth, is defined as the time between:

A)two successive appearances of the planet at its highest point in the observer's sky.
B)two successive passages of Earth through the vernal equinox.
C)conjunction and opposition on any orbit.
D)two successive passages through identical configurations, for example, two opposition positions.

Question 29

The time it takes for a planet to return to the same position with respect to the Sun and Earth in its orbit, such as the time from opposition to the next opposition, is known as:

A)1 year.
B)the planet's synodic period.
C)1 day.
D)the planet's sidereal period.

Question 30

How many more orbits around the Sun in 1 synodic period of that planet does an inferior planet cover compared to Earth?

A)wrong way around-Earth does one more orbit compared to the planet
B)two
C)one
D)a fraction of an orbit

Question 31

An imaginary planet is orbiting the Sun in a circle at precisely the same average orbital distance as Earth (i.e., 1 au). What is its sidereal period?

A)about 8/10 of a year
B)infinitely long
C)0
D)1 year

Question 32

What will be the synodic period of a (hypothetical) planet that orbits the Sun at exactly the same distance as does Earth?

A)2 years
B)0 years
C)1 year
D)infinitely long

Question 33

Copernicus's model for planetary motion:

A)got rid of epicycles entirely.
B)retained epicycles to reproduce retrograde motion.
C)retained epicycles to reproduce the observed variations in the speeds of the planets along their orbits.
D)retained epicycles but made them elliptical.

Question 34

If a particular asteroid with a circular orbit is seen at opposition every 1.44 years, then its sidereal period is:

A)0.59 years.
B)1.44 years.
C)0.44 years.
D)3.27 years.

Question 35

A spacecraft that has been put into a circular orbit around the Sun (in the same plane as Earth's orbit) with a sidereal period of 2.25 years is unobservable behind the Sun once every:

A)3.85 years.
B)2.25 years.
C)1.80 years.
D)1.00 years.

Question 36

What is the synodic period of Neptune? (See Table of Orbital Data in Appendix 1, Universe, 11th ed.)
​
​

A)367.5 days
B)367.5 years
C)84 years
D)165 years

Question 37

Approximately how many of its sidereal periods has Neptune completed since its discovery in 1846? (See Table of Orbital Data in Appendix 1, Universe, 11th ed.)
​
​

A)about 15
B)212
C)slightly more than 1
D)147

Question 38

The sidereal period of Mars is 1.9 years. Use the appropriate formula in Box 4-1 to find the time from the middle of one retrograde loop for Mars to the middle of the next retrograde loop (assuming circular orbits for Mars and Earth). This time is:

A)365 days.
B)694 days.
C)770 days.
D)1059 days.

Question 39

Earth moves eastward in its orbit around the Sun, and so does Mars. Suppose Mars moved westward rather than eastward. What result would this have on the retrograde motion of Mars as observed from Earth? (You might need to make a drawing similar to Figure 4-5 of Universe, 11th ed. to answer this question.)
​
​

A)Mars would not exhibit retrograde motion.
B)Mars would show retrograde motion, but less frequently than now.
C)Mars would show retrograde motion, but more frequently than now.
D)Mars would show retrograde motion with the same frequency it has now.

Question 40

Which of the following planets shows the smallest maximum western elongation when viewed from Earth?

A)Mercury
B)Venus
C)Mars
D)Jupiter

Question 41

If we could observe a planet in orbit around the Sun but very far away, as its distance approached infinity, its synodic period would approach:

A)infinity.
B)1 year.
C)22.7 years.
D)0 years.

Question 42

If we could observe a planet in orbit around the Sun but very far away, as its distance approached infinity, its sidereal period would approach:

A)infinity.
B)1 year.
C)22.7 years.
D)0 years.

Question 43

When is Venus at opposition?

A)once each year, 365 days
B)once each Venus year, 225 days
C)once each synodic Venus year, 584 days
D)never

Question 44

An inner planet is observed (through a telescope) to have a gibbous shape whenever it is close to:

A)inferior conjunction.
B)perihelion.
C)superior conjunction.
D)opposition.

Question 45

A planet has a sidereal period that is many times longer than its synodic period. This planet:

A)must be inside the orbit of Venus.
B)must be outside the orbit of Mars.
C)cannot exist since a planet's sidereal period cannot be longer than its synodic period.
D)might be anywhere in the solar system, since all sidereal periods are much longer than synodic periods.

Question 46

The astronomer who used parallax to show that the supernova of 1572 occurred at a large distance from Earth was:

A)Nicolaus Copernicus.
B)Galileo Galilei.
C)Johannes Kepler.
D)Tycho Brahe.

Question 47

Parallax requires the observation of a distant object from two different positions. How did Tycho Brahe accomplish this?

A)He developed a network of observers throughout Europe who were all instructed to make simultaneous observations on certain dates.
B)Knowing that any change would take a long time, he himself would make observations from different cities a few days apart.
C)He remained at one location and allowed the rotation of Earth over the course of a single night to shift his observation position with respect to the distant stars.
D)He remained at one location and allowed the motion of Earth in its orbit over the course of a few weeks to shift his observation position with respect to the distant stars.

Question 48

Tycho Brahe's most important contribution to the development of modern astronomy was the:

A)discovery of the satellites (moons) of Jupiter.
B)proof that planetary orbits are ellipses.
C)use of parallax to prove that Earth does not move.
D)accurate measurement of planetary positions.

Question 49

One of the important innovations in the work of Tycho Brahe was:

A)the use of the refracting telescope.
B)the simultaneous use of several telescopes in different locations to measure parallax.
C)making the same observation with different instruments to determine the size of instrumental error.
D)the use of statistics to summarize many repeated observations.

Question 50

An asteroid in the asteroid belt orbits the Sun at a distance of 2.8 au. Using Kepler's laws and the relation between an object's sidereal period and synodic period, determine the synodic period of this asteroid when observed from Earth.

A)2.01 years
B)1.27 years
C)1.56 years
D)4.68 years

Question 51

At what distance would a planet have to orbit the Sun to have its synodic period equal to its sidereal period, assuming circular orbits for Earth and the planet?

A)1.59 au
B)2 au
C)2.83 au
D)1 au, the same distance as Earth's orbit

Question 52

Kepler's laws describe the:

A)motions of the planets around the Sun.
B)motion of the spin axis of Earth over long time periods.
C)motions of the planets around Earth.
D)motion of the Moon around the Sun.

Question 53

The eccentricity of Venus's orbit is e = 0.007, while the eccentricity of Mars's orbit is e = 0.093. Thus, the:

A)orbit of Mars is closer to being circular than is the orbit of Venus.
B)orbit of Venus is closer to being circular than is the orbit of Mars.
C)orbits of all the planets are perfectular circular, so these values say nothing about the circularity of the orbits.
D)semimajor axis of Mars's orbit is smaller than that of Venus's orbit.

Question 54

The eccentricity of Venus's orbit is e = 0.007. Suppose a Planet X is discovered with an orbital eccentricity of e = 0.014. This tells us that:

A)this planet orbits inside the orbit of Venus.
B)this planet orbits outside the orbit of Venus.
C)the orbit of Venus is closer to being a perfect circle.
D)the orbit of Planet X is closer to being a perfect circle.

Question 55

In an ellipse, the semimajor axis is a distance measured:

A)along the circumference between the closest point to and the farthest point from one focus.
B)along the shorter diameter from the center to the ellipse.
C)from focus to focus.
D)along the longer diameter from the center through one focus to the ellipse.

Question 56

The planet Neptune moves fastest at what part of its elliptical orbit around the Sun?

A)conjunction
B)It always moves at a constant speed as required by Kepler's second law.
C)aphelion
D)perihelion

Question 57

How does the speed of a communications satellite vary as it moves around Earth?

A)It is slowest at perigee.
B)It is slowest at apogee.
C)It must have the same speed all the way around.
D)It slows continuously.

Question 58

Kepler's third law states that:

A)the orbital period of a planet is inversely proportional to the square of its mean distance from the Sun.
B)the cube of the orbital period is directly proportional to the square of its mean distance from the Sun.
C)the square of the orbital period is directly proportional to the cube of its mean distance from the Sun.
D)the orbital period of a planet is directly proportional to its mean distance from the Sun.

Question 59

According to Kepler's law, the approximate sidereal period of an asteroid moving around the Sun at a distance of about 2.8 au in the asteroid belt is:

A)46.8 years.
B)2.8 years.
C)1.99 years.
D)4.68 years.

Question 60

An asteroid orbits the Sun in a circle with a sidereal period of 11.9 years. Compare this with the orbital characteristics of the planets. At what equivalent distance will this asteroid orbit the Sun?

A)between the orbits of Saturn and Uranus
B)at an orbital distance beyond that of Pluto
C)at the same orbital distance as Jupiter
D)at the same orbital distance as Venus

Question 61

If an asteroid orbits the Sun in a circular orbit with a sidereal period of 11.9 years, how would this asteroid be classified? (See Chapter 15, Universe, 11th ed.)

A)normal asteroid, orbiting within the asteroid belt
B)meteoroid
C)Apollo asteroid
D)Trojan asteroid

Question 62

Halley's Comet returns to the Sun's vicinity every 76 years in an elliptical orbit. What is the semimajor axis of this orbit?

A)17.5 au
B)0.59 au
C)1 au
D)50.000 au

Question 63

Galileo's early observations of the sky with his newly made telescope included the:

A)fact that Venus showed phases similar to those of the Moon.
B)discovery of the aurora, or northern lights.
C)discovery of retrograde motion in planets.
D)discovery of Pluto.

Question 64

As Venus orbits the Sun, by what factor, as viewed from Earth, does its angular size change from smallest to largest? (See Figures 4-13 and 4-14, Universe, 11th ed.(in the text))

A)Only brightness changes; angular size does not.
B)1.72
C)58
D)5.8

Question 65

Galileo Galilei died in the same year that saw the birth of:

A)Ptolemy.
B)Copernicus.
C)Newton.
D)Einstein.

Question 66

Which one of the following relationships represents Newton's most important contribution to physics?

A)the relationship between gravity and distance
B)the relationship between velocity and acceleration
C)the relationship between mass and weight
D)the relationship between force and motion

Question 67

To specify an object's speed, we need to specify:

A)only how fast it is moving.
B)only the direction in which it is moving.
C)how fast it is moving and also its mass.
D)how fast it is moving and also the direction in which it is moving.

Question 68

Acceleration of a body is the rate of change with time of its:

A)mass.
B)weight.
C)position.
D)velocity.

Question 69

To which of these phenomena do Newton's laws of motion not apply?

A)a high jumper at the Olympic Games
B)a spacecraft in circular orbit around Earth, such as communication satellites
C)a beam of light traveling between the Sun and Earth
D)space vehicles on a journey to Jupiter (e.g., Galileo)

Question 70

A certain object at rest on the surface of Earth has a weight of 49 newtons. Its mass is, therefore:

A)49 kg.
B)49 newtons.
C)5.0 kg.
D)0.20 newtons.

Question 71

When several objects with different masses are dropped by an astronaut on the (airless) Moon where there is no air friction, their resultant motions:

A)depend on densities of the objects, the one with the highest density falling fastest.
B)depend on masses of the objects, the lightest falling fastest.
C)depend on the masses of the objects, the most massive falling fastest.
D)are independent of the masses of the objects.

Question 72

Two objects of different mass when dropped by an astronaut on the Moon have:

A)no acceleration at all in the airless space.
B)the same acceleration.
C)different accelerations proportional to their masses.
D)different accelerations, the more massive object having the smaller acceleration.

Question 73

Newton's second law states that acceleration produced by a force is:

A)inversely proportional to the square of the mass on which the force acts.
B)independent of the mass on which the force acts.
C)proportional to the mass on which the force acts.
D)inversely proportional to the mass on which the force acts.

Question 74

Newton, in his second law of motion, stated that any body of mass m acted on by a force F:

A)will be given an acceleration a, of size a = F/m.
B)will also have acting on it an equal and opposite force, ma, where F = ma, and a is the acceleration.
C)will remain at rest, unless a second force also acts on the body.
D)moves with a constant velocity, in the direction of the force.

Question 75

Two spacecrafts that have different masses but rocket engines of identical force are at rest in space. If they fire their rockets at the same time, which ship will speed up fastest?

A)They will not speed up at all but will move at a constant speed since they are in space and the rocket has nothing against which to push.
B)The one with the lower mass will speed up fastest.
C)They will increase speed at the same rate since they have identical rocket engines.
D)The one with the higher mass will speed up fastest.

Question 76

If you drop an object near Earth's surface it will have an acceleration of 9.8 m/s². If, instead, you throw the object downward, its acceleration (after it leaves your hand) will be:

A)less than 9.8 m/s².
B)9.8 m/s².
C)more than 9.8 m/s².
D)some value that depends on the velocity of the object as it leaves your hand.

Question 77

When an object moves uniformly at a constant speed in a circle, the acceleration of the object is always:

A)outward, away from the center of the circle.
B)zero; the object is not accelerating, since it is moving uniformly at a constant speed.
C)inward, toward the center of the circle.
D)along the direction of the path, tangential to the circle.

Question 78

If a planet moves around the Sun in a circular orbit, how many forces act on it?

A)two forces, one toward the Sun, the other along the direction of motion
B)one force toward the Sun
C)two equal and opposite forces along the direction to the Sun
D)one force in the direction of motion

Question 79

A body moves through space with a certain speed. How many forces are needed to make this object move in a circle?

A)two, one inward, the other outward away from the center of the circle
B)only one force along the circular path and tangential to it
C)two, one inward toward the center of the circle, the second tangential to the circle to keep the object moving
D)only one, toward the center of the circle

Question 80

Imagine a 10-kg rock speeding through empty space at 200 m/s, so far away from other objects that there is no gravitational force (or any other outside forces) exerted on the rock. What is the rock's subsequent motion?

A)The rock will continue to move in a straight line at 200 m/s.
B)The rock will slow down and eventually stop.
C)The rock will go into an elliptical orbit.
D)The rock will go into a circular orbit.