Astronomy Chapter 2

True or False If the mass of a body were doubled, its gravity would become 4 times stronger.

False

True or False Newton's Laws completely replaced the incorrect work of Kepler.

False

Tycho Brahe's contribution to Kepler's Laws of Planetary Motion was: a. his detailed and accurate observations of the planet's position. b. his observations of Jupiter's moons. c. a mathematical explanation of epicycles. d. a precise lunar calendar. e. the correct explanation of lunar phases.

a. his detailed and accurate observations of the planet's position

Kepler's first law worked, where Copernicus' original heliocentric model failed, because Kepler described the orbits as: a. around the Sun, not the Earth. b. much larger than Copernicus had envisioned. c. being on equants instead of epicycles. d. elliptical, not circular. e. complex, with epicycles to account for retrograde motions.

d. elliptical, not circular

The place in a planet's orbit that is closest to the Sun is called: a. vernal equinox b. aphelion. c. crossing the ecliptic. d. perihelion. e. None of these; a planet's distance from the Sun never changes.

d. perihelion

A planet whose distance from the Sun is 3 A.U. would have an orbital period of how many Earth-years? a. 9 b. square root of 3 c. 3 d. square root of 27 e. 81

d. square root of 27

Kepler's third law is best expressed as ________.

P^2~a^3

See website

See website

The most famous prehistoric astronomical observatory is:

Stonehenge

True or FAlse Newton's modification of Kepler's Third Law lets us measure the mass of the Sun.

True

True or False A planet (or comet) will speed up as it approaches the Sun.

True

True or False According to Newton's second law, if you double the force acting on a body, the acceleration will double.

True

True or False Galileo's observations of the entire phase cycle of Venus proved that Ptolemy's epicycles could not be correct in keeping Venus between us and the Sun.

True

True or False It was the Chinese who provided critical ancient data on supernovae and comets.

True

True or False Kepler found the orbits of planets are ellipses, not circles.

True

True or False Mercury, with a higher eccentricity orbit, should change its orbital speed more than do Venus or Earth.

True

True or False The orbits of most of the planets in our solar system have eccentricities close to zero.

True

True or False When a planet retrogrades, it appears to move westward for weeks at a time.

True

True or False Like the Sun and the Moon, the stars appear to move from west to east from one day to the next.

True

True or False Kepler based his theories on the precise planetary observations of Tycho Brahe.

Truw

The Ptolemaic model probably persisted for all these reasons EXCEPT: a. it accounted well for Galileo's observations of the phase cycle of Venus. b. it explain why stellar parallax was not observed by the Greeks. c. it had the authority of Aristotle behind it. d. it was consistent with the doctrines of the Catholic Church. e. it used perfect circles, which appealed to geometry.

a. it accounted well for Galileo's observation of the phase cycle of Venus

Which of these was NOT a telescopic discovery of Galileo? a. the moons of Saturn b. the craters and mare of the Moon c. the four largest moons of Jupiter d. sunspots and the rotation of the Sun e. the phases of Venus

a. the moons of Saturn

Which was a contribution to astronomy made by Copernicus? a. He discovered the Sun was not at the center of the Milky Way. b. He laid out the order and relative motion of the known solar system. c. His telescope revealed the four moons of Jupiter, a model solar system. d. His theory of gravity accounted for the variable speeds of the planets. e. The planets move around the Sun in elliptical orbits.

b. He laid out the order and relative motion of the known solar system

Which of the statements below is part of both the Ptolemaic and Copernican models? a. Venus' epicycle must always lie between us and the Sun. b. The Moon orbits the Earth once a month. c. Epicycles are needed to explain retrograde motion of the planets. d. The Sun lies in the center of the Cosmos. e. The Earth orbits the Sun once a year.

b. The Moon orbits the Earth once a month

If the distance between two asteroids is doubled, the gravitational force they exert on each other will: a. be four times greater. b. be one fourth as great. c. also be doubled. d. be half as great. e. be 1/16 as great.

b. be one fourth as great

As shown in Figure 2.12 in the textbook ("Venus Phases"), Galileo's observations of Venus demonstrated that Venus must be a. about the same b. diameter as Earth. b. orbiting the Sun. c. similar to the Moon. d. orbiting Earth.

b. orbiting the Sun

Scientists today do not accept the Ptolemaic model because: a. it has been shown that Ptolemy faked his data. b. the work of Tycho and Kepler showed the heliocentric model was more accurate. c. it is ancient history. d. it had no explanation for retrograde motion. e. it was too complicated, compared to Copernicus' heliocentric model.

b. the work of Tycho and Keple showed the heliocentric model was more accurate

It took two centuries for the Copernican model to replace the Ptolemaic model because: a. the Church wouldn't let anyone talk about Copernicus' model for 200 years. b. there was no scientific evidence to support either model until Galileo made his observations. c. in Copernicus' time, there were no telescopes. d. the Ptolemaic model was simpler and more aesthetically pleasing. e. the Copernican model required complicated new terms to explain it correctly

b. there was no scientific evidence to support either model until Galileo made his observations

A calculation of how long it takes a planet to orbit the Sun would be most closely related to Kepler's a. first law of orbital shapes. b. third law of planetary distances. c. first law of inertia. d. second law of orbital speeds.

b. third law of planetary distances

Which concept was NOT a part of Kepler's Laws of Planetary Motion? a. The square of the planet's period is equal to the cube of its average distance. b. A planet must move fastest in its orbit at perihelion. c. Epicycles are needed to explain the varying brightness of the planets. d. All planetary orbits are ellipses.

c. Epicycles are needed to explain the varying brightness of the planets

The principal culture that transferred Greek astronomical knowledge to Renaissance Europe was: a. Byzantine. b. Mongol. c. Islamic. d. Chinese. e. Mayan.

c. Islamic

What does Kepler's third law imply about planetary motion? a. Planets further from the Sun orbit at a faster speed than planets closer to the Sun. b. Planets closer to the Sun orbit at a slower speed than planets further from the Sun. c. Planets further from the Sun orbit at a slower speed than planets closer to the Sun. d. All planets orbit the Sun at the same speed. e. This law implies nothing about a planet's motion.

c. Planets further from the Sun orbit at a slower speed than planets closer to the Sun.

The force of gravity between two objects: a. depends on the density, not the mass of the bodies. b. increases with the masses of the bodies, but decreases with their separations. c. increases with the masses of the bodies, but decreases with the square of the distances between them. d. increases with the square of their masses, but decreases with the cube of their periods of orbit about the Sun. e. depends on the temperature, density, and size of the bodies.

c. increases with the masses of the bodies, but decreases with the square of the distances between them

Escape velocity is the speed required to: a. orbit an object. b. keep from falling out of orbit around an object. c. overcome the gravitational pull of an object. d. overtake an object in orbit and pass it. e. maintain a constant distance from an object.

c. overcome the gravitational pull of an object

A circular orbit would have an eccentricity of: a. infinity. b. between 0 and 0.5. c. exactly 1.0. d. 0. e. between 0.5 and 1.

d. 0

Compared to orbital velocity, escape velocity is about: a. twice as large. b. four times greater. c. 70% less. d. 40% more. e. the same.

d. 40%

Kepler's second law implies what about planetary motion? a. A planet moves faster when it is farther from the Sun. b. This law implies nothing about a planet's motion. c. A planet moves slower when it is closer to the Sun. d. A planet moves faster when it is closer to the Sun. e. A planet moves at a constant speed during its orbit of the Sun.

d. A planet moves faster when it is closer to the Sun

Which of the following was NOT a contribution of Galileo to astronomy? a. Sunspots showed the Sun was rotating on its axis, like the Earth does. b. The four moons of Jupiter are a model for the solar system motions in general. c. The phases of Venus prove it orbits completely around the Sun. d. The changing appearance of Saturn's rings corresponds to our seasons. e. The craters and mare of the Moon prove it a world in its own right.

d. The changing appearance of Saturn's rings corresponds to our seasons.

According to Newton's Law of Universal Gravitation, if the Moon were three times further from Earth, the force by Earth on the Moon would: a. stay the same. b. decrease by a factor of 3. c. increase by a factor of 9. d. decrease by a factor of 9. e. increase by a factor of 3.

d. decrease by a factor of 9

Orbital speed is the speed with which a planet moves around the Sun. This speed is determined by: a. both the mass of the planet and the mass of the Sun. b. the mass of the planet and its distance from the Sun. c. the mass of the Sun only. d. the mass of both the planet and the Sun and the distance between the two. e. the mass of the planet only.

d. the mass of both the planet and the Sun and the distance between the two

During the eighteenth and nineteenth centuries, attempts to precisely measure the astronomical unit relied largely on rare: a. passages of comets close to the Earth. b. oppositions of Mars. c. maximum elongations of Venus. d. transits of the inferior planets across the Sun. e. total solar eclipses.

d. transits of the inferior planets planets across the Sun

Which of the following is a contribution to astronomy made by Galileo? a. Venus appears almost fully lit when it lies on the far side of the Sun. b. The astronomical telescope can show us far more detail than the eye can. c. Jupiter has four moons orbiting it. d. The Moon has craters, mountain, valleys, and dark flat areas on its surface. e. All of the above.

e. All of the above

On which of these assumptions do Ptolemy and Copernicus agree? a. The Sun was bigger than the Earth. b The Earth must be the center of all motion in the Cosmos. c. The Sun must orbit us, but the planets do orbit the Sun. d. Venus must always stay between us and the Sun. e. All orbits must be perfect circles.

e. All orbits must be perfect circles

The force of gravity varies with the: a. product of the two masses. b. inverse of the distance separating the two bodies. c. inverse square of the distance separating the two bodies. d. Both A and B are correct. e. Both A and C are correct.

e. Both A and C are correct

A fatal flaw with Ptolemy's model is its inability to predict the observed phases of: a. Jupiter and Saturn. b. Mars and Jupiter. c. the Moon in its monthly cycle. d. the Sun during an eclipse. e. Mercury and Venus.

e. Mercury and Venus

Galileo found the rotation period of the Sun was approximately: a. a year. b. three months. c. a week. d. a day. e. a month.

e. a month

According to Copernicus, retrograde motion for Venus must occur around: a. superior conjunction, when the planet is on the far side of the Sun. b. greatest elongation, when the planet is farthest from the Sun. c. opposition, when the planet lies opposite the Sun in the sky. d. quadrature, when the planet is 90 degrees away from the Sun. e. inferior conjunction, when it passes between us and the Sun.

e. inferior conjunction, when it passes between us and the Sun

Today we rely largely on what technique to precisely measure distances in the solar system? a. transits of Venus across the Sun b. precise measurements of length of the year with atomic clocks c. timings of the eclipses of its moons by Jupiter's shadow d. measurement of stellar parallaxes. e. radar echo timings

e. radar echo timings

The greatest contribution of the Greeks to modern thought was: that their mythology was the basis for the naming of the constellations. the invention of the telescope. that their observation of stellar parallax proved the Earth orbited the Sun. the idea that all the planets orbited the Sun. the development of scientific inquiry and model building.

e. the development of scientific inquiry and model building

How long would a radar signal take to complete a round-trip between Earth and Mars when the two planets are 0.7 AU apart? Express your answer using two significant figures.

t=700 seconds