INST 2403
STUDY GUIDE for Midterm 2
FALL 2014
Form of Exam
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About 35 questions
Mostly multiple choice
Few short answer question
You have the whole class period; this should be ample time
Scantron sheets are used
Topics (also see syllabus)
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Triangulation & measurements
History of Astronomy
Ptolemy & Copernicus
Galileo, Phases of Venus
Kepler, Laws of Planetary motion
Newton, 3 Axioms, Law of universal Gravity
Quantitative reasoning, scaling, algebraic statements
Solar System overview, terrestrial planets, the moon
No Greenhouse Effect!
Suggestions
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Review textbook readings, online Powerpoint slides
Revisit the Warm-Up questions
Look over the activities
Take another look at the homework questions. In particular, take a look at the solutions
after you committed to an answer
It might help to go to the library and study other astronomy texts. Often reading an
independent explanation in slightly different wording helps to understand a complex
concept.
Sample Questions
1. How did Jupiter’s location in the solar system affect its composition?
a. Jupiter is rich in metals because only metallic grains could survive the low
temperatures far away from the sun
b. Jupiter is poor in metals because metallic grains cannot withstand these low
temperatures
c. Because Jupiter is so far away from the sun, it could hold on to volatile substances,
such as helium and hydrogen
d. None of the above
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2. How would the strength of the force between Saturn and the Sun change if Saturn were ten
times closer to the Sun?
a. It would not change.
b. It would be ten times as large.
c. It would be ten times smaller
d. It would be 29 times larger.
e. It would be one hundred times larger.
3. The mass of the Moon is 80 times smaller than that of Earth. How does the strength of the
gravitational force that the Earth exerts on the Moon compare to the gravitational force that
the Moon exerts on Earth?
a) It is 80 times smaller.
b) It is 80 times bigger.
c) It is 6400 times smaller.
d) None of the above.
4. Approximately how long is a Saturn year, i.e. the time that it takes Saturn to orbit once
around the sun? (Hint: Saturn is 9.5 AU away from the sun, and Kepler’s 3rd law states that
P2/a3=1.)
a. 2 years
b. 5 years
c. 12 years
d. 29 years
e. 84 years
5. An ion tail of a comet always points
a. directly away from the sun.
b. directly toward the sun.
c. at an angle of 90 degrees to the sun direction.
d. There is no preferred direction.
6. You visit a planet that rotates on its axis in 3 hours, while it revolves closely around its sun
every 61 hours. You construct for the inhabitants an excellent calendar with a leap year that
occurs once every ...
a. 2 years.
b. 3 years.
c. 4 years.
d. 61 years.
e. None of the above.
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Short Answer Questions [3 points each]
(Please use the back side of the computer sheet to record your answers)
7. Explain Kepler’s second law in your own words. (Merely restating it won’t garner any points.)
8. Why do the planets have (almost) circular orbits around the Sun, even though the gravitational
force of the Sun points exactly at the Sun, i.e. works to pull the planets closer to the Sun? Argue
with Newton’s laws.
9. How did Galileo’s observation of the phases of Venus enable him to rule out the geocentric
theory?
List of Warm-Up Questions
Warm-up #11: based on reading from course webpage: “The Trial of Galileo”
1. What has Aristotle to do with the religious beliefs at the time of Copernicus and later Galileo?
2. Explain the difference between the heavenly and the earthly realm in the view of people in the
renaissance.
Warm-up #12: based on Section 1.1. “Motion of the Planets”
1. Describe the Ptolemaic model of the solar system.
2. Why did Ptolemy have to use epicycles?
3. Why did Copernicus have to use epicycles?
Warm-up #13: based on Section 1.2. “The Birth of Modern Astronomy”
1. In which ways were Galileo’s telescopic observations at odds with Aristotelianism? Do not
just state some things he observed, but explain why these observations are at odds with the
Aristotelian world view.
2. Name one specific observation you could be making to falsify Ptolemy’s model of the solar
system, and describe why his model cannot reproduce this pattern in the sky.
Warm-up #14: based on Section 1.3. “The Laws of Planetary Motion”
1. In what way is an ellipse the generalization of a circle?
2. Did Kepler succeed in finding the distance to the Sun? Why or why not?
Warm-up #15: based on the course webpage reading on Descartes’ “Discours de la méthode
pour bien conduire sa raison, et chercher la vérité dans les sciences”
1. Describe, in your own words, the four principal rules of Descartes’ method of rightly
conducting one's reason and of seeking truth in the sciences.
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Warm-up #16: Based on the Arons article linked on the course homepage.
1. What are the two types of knowledge mentioned in the text? Give an example for each.
2. Why is Kafka mentioned in this text about scientific literacy?
Warm-up #17: based on 1.4 “Newton’s Laws”
1. What is the relation of Newton’s laws to Kepler’s laws?
2. Describe the circle of scientific progress that is inherent in the advances of our understanding
of the laws of planetary motion as associated with the names Ptolemy, Copernicus, Brahe,
Kepler and Newton. Do NOT just state who did what!
Warm-up #18: based on “Newton’s Cannon” simulation
(http://galileo.phys.virginia.edu/classes/109N/more_stuff/Applets/newt/newtmtn.html)
1. Describe what happens if you fire the cannon with (approximately) 10000mph, 17000mph,
19000mph and maximal velocity.
2. Using the simulation, explain how Newton “unified” the theories describing the sublunar and
the superlunar spheres of Aristotle, i.e. why did Newton come up with this illustration?
Warm-up #19: based on Chapter 4 “The Solar System”
1. Give an *operational* definition of the main types of objects in the solar system, i.e. explain
how objects in these categories differ: star, terrestrial planet, jovian planet, comet, asteroid,
meteoroid.
Warm-up #20: based on Sections 4.3, 5.1 & 5.2
1. Briefly describe what the theory of solar system formation has to say about the existence of
the two categories of planets (terrestrial and Jovian).
2. Why are there *two* tidal bulges, if the effect comes largely from *one* moon?
Warm-up #21: based on Chapters 5.6 – 5.8
1. How can the amount of cratering be used to say something about the age of the surface of the
moon?
2. How did the Earth-Moon system form and evolve?
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