# Part I Multiple Choice. Choose the best answer for

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```							     ASTR 0101: Astronomy
Spring Semester, 2009
Midterm Exam                                             Name: ______________________________

Part I: Multiple Choice. Choose the best answer for each multiple choice question and circle the
corresponding letter. You should circle only one letter for each question. If you change your mind, be
sure to indicate clearly your final choice - no credit will be given for ambiguously marked questions.
Each question is worth 2 points.

1.   A “dirty snowball several kilometers (or miles) in diameter” would be a reasonable description of
a) an asteroid
b) Pluto
c) a comet
d) Westfield

2.   The physicist/astronomer who was the first person to use a telescope (in 1609, exactly 400 years ago!!)
to systematically observe the night sky, and whose discovery of the phases of Venus showed
conclusively that the geocentric model was incorrect, was
a) Galileo Galilei
b) Isaac Newton
c) Nicolaus Copernicus
d) Tycho Brahe

3.   The terrestrial planets ----- than the jovian planets.
a) are larger in diameter
b) have more moons
c) spin faster
d) have higher densities

4.   Since they were first observed in the 1600s, the number of sunspots on the sun’s photosphere has
c) varied cyclically, with about an 11-year cycle
d) varied cyclically, with about a 35-year cycle

5.   According to Kepler's laws, the orbits of the planets around the sun are generally
a) hyperbolas
b) circles
c) parabolas
d) ellipses

6.   If the distance between the Earth and sun were doubled, then the gravitational force between them
would (Hint: see the list of equations on the bottom of p. 5)
a) also double (increase by a factor of 2)
b) be cut in half (decrease by a factor of 2)
c) quadruple (increase by a factor of 4)
d) be reduced to ¼ its original value (decrease by a factor of 4)
Astronomy (S09)                            Midterm Exam                                Page #2 of 6

7.   A total solar eclipse can occur only when
a) the sun appears on the celestial equator
b) the moon is new
c) the sun is transiting
d) the moon is full

8.   Mercury’s surface is heavily cratered, suggesting that
a) Mercury was once very volcanically active
b) Mercury’s surface is very old
c) Mercury formed long before the sun, and was later captured by the sun’s gravity
d) Mercury has a strong greenhouse effect

9.   Mike exerts a force of 50 N eastward against a desk, while Joe exerts a force of 40 N westward against
the same desk. The net force acting on the desk is
a) 10 N eastward
b) 10 N westward
c) 90 N eastward
d) 90 N westward

10.   The color of a star is primarily an indication of the star’s
a) mass
b) surface temperature
c) chemical composition
d) WHOAA!! - all stars are the same color!

11.   In order of increasing size, from smallest to largest, the Earth belongs to the following "systems":
a) Milky Way galaxy, Local Group, solar system
b) solar system, Local Group, Milky Way galaxy
c) Local Group, solar system, Milky Way galaxy
d) solar system, Milky Way galaxy, Local Group

12.   The moon orbits the Earth approximately once every
a) day
b) week
c) month
d) year

13.   The sketch at the right shows the orbit of Ganymede around Jupiter. The
direction of the net force acting on Ganymede at the location shown would be
a) A
b) B
c) C
d) WHOAA!! - the net force on Ganymede would be zero!

14.   If you multiply (2 x 1013 m) by (3 x 104 N), you'd get
a) 6 x 1017 m N
b) 6 x 1017 m / N
c) 6 x 1052 m N
d) 6 x 1052 m / N
Astronomy (S09)                            Midterm Exam                                Page #3 of 6

15.   Of the following sets of conditions for a planetary surface, the set that would most favor the retention of
a thick atmosphere is
a) strong surface gravity, and high surface temperature
b) strong surface gravity, and low surface temperature
c) weak surface gravity, and low surface temperature
d) weak surface gravity, and high surface temperature

16.   The sun, moon, and planets are always found near the ----- in the sky.
a) meridian
b) celestial equator
c) horizon
d) ecliptic

17.   According to Newton's laws of motion, if the net force acting on an object is zero, then the object's -----
will also be zero.
a) speed
b) kinetic energy
c) acceleration
d) all of the above

18.   Suppose that astronomers discovered an object in space whose thermal radiation peaked in the γ-ray
(gamma-ray) portion of the electromagnetic spectrum. They’d naturally infer that the object was
a) incredibly far away
b) incredibly hot
c) incredibly old
d) incredibly massive

19.   Polaris is “special” because
a) it’s the only fairly bright star that doesn’t move during the night
b) it’s the brightest star in our night-time sky
c) it’s located at the center of the Milky Way galaxy
d) all of the above

20.   In order of increasing distance from the sun (from nearest the sun to farthest away), the planets of our
solar system include
a) Venus, Mars, Saturn
b) Mars, Venus, Saturn
c) Saturn, Mars, Venus
d) Mars, Saturn, Venus

21.   Consider the diagram at the right, which shows the sun, Earth, and Jupiter.
When those objects are in the positions shown, an observer on Earth
would see Jupiter as approximately
a) new
b) full
c) either 1st or 3rd quarter
d) WHOAA!! - Jupiter doesn't have any phases!
Astronomy (S09)                           Midterm Exam                                Page #4 of 6

22.   The dark band in the outer portion of Saturn’s rings, known as the -----, is a region within which few
ring particles orbit Saturn.
a) Kuiper Belt
b) Kirkwood Gap
c) Cassini Division
d) Asteroid Belt

23.   An object whose spectrum displays a “redshift” must be
a) getting hotter
b) moving toward us
c) getting cooler
d) moving away from us

24.   Stars that always remain above our horizon, never rising or setting, are called
a) geocentric
b) circumpolar
c) zodiacal
d) WHOAA!! - all stars rise and set daily!!

25.   During a meteor shower
a) you might see dozens of “shooting stars” per hour
b) you are seeing “sand-sized” rocky particles “burning up” in Earth’s atmosphere
c) the Earth is passing through the debris left behind by a comet
d) all of the above

Part II. Short Answer: Answer any 3 of the following 4 questions. Two to four sentences should
generally be sufficient, but be sure to give a complete answer. For numerical problems, be sure to
show all your work: the equation you used, how you solved it (if necessary), the values (with units)
you plugged in, and the final answer with units. Each question is worth 5 points.

1.   The sun constantly radiates enormous amounts of energy in the form of light. What is the source of all
that energy? Explain.
Astronomy (S09)                           Midterm Exam                                   Page #5 of 6

2.   Earth's orbit around the sun is approximately circular, with a radius of about r = 1.5 x 108 km. Given
that the circumference of a circle is C = 2πr, and that 1 year ~ 3 x 107 s, calculate the speed at which the
Earth moves along its orbit. Feel free to round off to simplify your calculation.

3.   What is the “greenhouse effect” and how does it work?

4.   Name one celestial object that undergoes "retrograde motion", describe that motion, and explain briefly
why it happens.

Possibly Useful Information

v=d/t                          a = Fnet / m                   KE = ½ m v2
PE = m g h                     Fgrav = GM1M2 / d2             P2 = k a3
c=fλ                           E = m c2                       c = 3 x 108 m/s
Astronomy (S09)                          Midterm Exam                                Page #6 of 6

Part III. Short Essay: Answer either of the following questions. Use complete sentences and
compose your response carefully - the mark is based on clarity of expression as well as content. Two or
three good paragraphs should suffice, but be sure to give a complete answer. This question is worth 10
points.

1.   Briefly explain the five processes of science as discussed in class this semester. Use the historical
events surrounding the replacement of the geocentric model by the heliocentric model to provide an
example for each of the five processes.

2.   Briefly describe the process by which astronomers think our solar system formed. What are two
"regularities" of the solar system that can be explained by that process, and how does the process you've
described actually explain those "regularities"?
Astronomy (S09)                         Midterm Exam                               Page #7 of 6

5.   The Orion Nebula is a “cloud” of gas in space that’s being heated by young stars forming within it.
What “type” of spectrum would you see if you looked at the light from the nebula with a spectroscope,
and what is one thing you could learn about the nebula from it’s spectrum. Explain.

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