Homework Set #2
Astronomy 1002




1. What is the importance of Kepler's first law?

A. It fully explains the motion of bodies in the solar system.

B. It shows that the Greek notion of circular motion was wrong.

C. It explains retrograde motion.

D. It gave the first explanation of gravity.

E. It provided a way to determine the distances to planets.


2. What was the importance of Kepler's second law?

A. It showed that orbits are ellipses.

B. It provided a way to determine the distances to planets.

C. It provided an understanding of the concept of the force.

D. It shows that planets do not move uniformly in their orbits.

E. It shows that the Greek notion of circular motion was wrong.


3. What was the importance of Kepler's third law?

A. It gives the relative distances of the planets from the Sun.

B. It gives the relative distances of the planets from the Earth.

C. It says that forces act in pairs and in opposite directions.

D. It explains why projectiles shot northward always fall to the east

of the target.

E. It provided for the first observation of stellar parallax.


4. Freddy's Comet is an impressive naked-eye comet that was seen in 1977 and 1985 (and not in between). What is the comet's average distance from the Sun?

A. 1 AU

B. 2 AU

C. 4 AU

D. 8 AU

E. Can not be determined from the information given


5. Which of the following was -not- an observational discovery of Galileo?

A. the period of rotation of the Sun

B. the gibbous phase of Venus

C. the motions of the satellites of Jupiter

D. the aberration of light

E. the Milky Way being made of large numbers of faint stars


6. Why could serious thinkers of the time object to the new theories put forth by Copernicus?

A. His heliocentric model could not explain retrograde motion.

B. It did not explain the aberration of light.

C. Kepler had already demonstrated that the orbits were not circles.

D. His circular orbits did not reproduce planetary positions as well as the established Ptolemaic system did.

E. It violated the physics of Aristotle.


7. What was Tycho Brahe's principal contribution to astronomy?

A. his open support of the Copernican model of the cosmos.

B. his suggested model for the solar system (which had a fixed Earth with the Sun revolving about it but the rest of the plane revolving about the Sun).

C. his choice of Galileo as an assistant.

D. the accuracy of his observations and the completeness of his records.

E. etiquette lessons on drinking large quantities of alcohol at important social functions.


8. Who was the scientist who first suggested that the Earth circles the Sun and found the relative sizes of the Earth, Moon, and Sun?

A. Aristarchus.

B. Hipparchus.

C. Ptolemy.

D. Copernicus.

E. Eratosthenes.


9. Who described the characteristics of an earth-centered universe in a book called the ALMAGEST?

A. Aristarchus.

B. Aristotle.

C. Copernicus.

D. Hipparchus.

E. Ptolemy.


10. What is the mean distance from the Sun of a planet whose period of revolution is 5 years?

A. impossible to calculate without knowing the eccentricity

B. 5 AU

C. 125 AU

D. square root of 125 AU

E. cube root of 25 AU


11. What observations was Ptolemy trying to explain with the use of the geometrical device of the epicycle?

A. motion of sky east to west in 24 hours

B. non-uniform motion of sun, west to east, along ecliptic in 1 year

C. motion of planets west to east compared to stars

D. retrograde motion of planets

E. distances between planets


12. What geometrical devices did Ptolemy use to explain the variations in retrograde motion of the planets?

A. equant

B. eccentric

C. epicycle

D. both a and b

E. both a and c


13. What force keeps the planets moving around the sun in the Copernican cosmos?

A. gravity

B. magnetism

C. none, orbital motion is natural

D. etherial drag


14. Why did Tycho Brahe object to the new theories put forth by Copernicus?

A. Tycho was not able to observe stellar parallax.

B. Tycho arrogantly thought no one was smarter than he and so he

didn't believe anyone else's theories.

C. Copernicus' model did not predict planetary motions as well as the

Greek geocentric models.

D. Tycho did not believe in the physics of Aristotle.


15. What ancient culture believed that the earth had no shape, the stars were attached to a shell and that the sun entered and left through a gate?

A. Babylonian

B. Egyptian

C. Indian

D. Chinese

E. Greek


16. Copernicus explained the retrograde motions of the planets

A. as natural motions

B. using epicycles and deferents

C. using equants and eccentrics

D. as resulting from the relative motions of the planets and earth

around the Sun

E. as a result the planet's orbits around the earth


17. What Ancient Greek Astronomer determined the size of the earth?

A. Aristarchus

B. Ptolemy

C. Pythagoras

D. Aristotle

E. Erastothenes


18. Why was Galileo's observation that Venus may be seen in a gibbous phase important?

A. It proved that the theory of Copernicus was 100% correct.

B. It proved that at least Venus orbited the Sun

C. It demonstrated that Venus was more distant from the Sun than the Earth

D. It showed that Venus had and elliptical orbit.

E. It showed that Venus deviated from the ecliptic as it orbited


19. Why does an astronaut float inside the space shuttle?

A. Because there is no gravity in space.

B. Because the pull from the moon equalizes the pull from the Earth.

C. Because the astronaut's orbital motion cancels out the force of


D. Because both the astronaut and the shuttle are falling toward the


E. Because uniform forces from the cylindrical shuttle are the same on all sides of the astronaut, cancelling out and making the astronaut appear to float.


20. Suppose the Earth started spiraling in towards the Sun. As the orbit got smaller, what would happen to the speed of the Earth in its orbit?

A. It would stay the same.

B. It would go faster.

C. It would go slower.

D. There is not enough information to answer the question.


21. What concept is the motion of a rocket blasting off an example of?

A. conservation of angular momentum

B. F=ma

C. inertia

D. conservation of mass and energy

E. for every action there is an equal and opposite reaction


22. If something were to cause the Earth to squeeze all its mass down into a ball only one-tenth the size of the present Earth, what would happen to the orbit of the Moon?

A. The smaller Earth could not hold onto the Moon, and it would go

flying away.

B. The smaller Earth would generate a stronger force on the Moon.

C. The Moon orbit would become more elliptical.

D. You would need more than Newton's laws to say what would happen.

E. Nothing, since all of the numbers in the equation for gravitational force on the Moon would stay the same.


23. Newton's modification of Kepler's 3rd law is useful because it allows astronomers to determine _____.

A. surface gravity

B. distance

C. diameter

D. mass

E. rotation period


24. If the distance between two masses is doubled, what happens to the force between them?

A. It stays the same.

B. It increases by a factor of two.

C. It increases by a factor of four.

D. It decreases by a factor of two.

E. It decreases by a factor of four.


25. A space probe is boosted by a rocket until it is out of the solar system. In deep space, away from all stars, the rocket engine stops. What will happen to the space probe?

A. It will slow down and comes to rest.

B. It will continue with constant acceleration in a straight line.

C. It will move at a speed depending upon its temperature.

D. It will eventually reverse in direction and return to the Earth.

E. It will cruise in a straight line at constant speed.


26. What do we find when we compare the effect of the Earth's gravity on the Moon with the effect of the Moon's gravity on the Earth?

A. The forces are the same but Moon's acceleration is less.

B. The force on Moon is greater, but acceleration is the same.

C. The forces are the same, but Moon's acceleration is greater.

D. The force on Moon is less, but its acceleration is greater.

E. The force on Moon and Moon's acceleration are greater.


27. The mass of the Earth can be determined using the Moon and by applying

A. Newton's first law of motion.

B. Newton's form of Kepler's 3rd law of planetary motion.

C. Newton's form of Kepler's first law of planetary motion.

D. Newton's 3rd law.

E. Brahe's first law.


28. The Ptolemaic picture of the universe probably survived for so long because:

A. It is correct.

B. It is consistent with the doctrines of the Church.

C. It worked well in explaining the motions of the planets.

D. It was based on precise measurements of planetary positions.


29. What was one of Newton's contributions to astronomy?

A. He discovered that the planets move around the Sun in elliptical orbits.

B. He developed a theory of gravity that could explain orbital motion.

C. He said that the Earth is not at the center of the universe.

D. He used a telescope to observe the heavens, thereby reinforcing the notion of heliocentricity.

E. He made extensive and detailed observations of the positions of planets.