Download Sample exam 1

Astronomy 100
Sample exam 1
Open textbook, notes, handouts, calculator; closed other textbooks; no collaboration.
This exam is worth 50 points and is timed for fifty minutes.
Short answer
1. Who will you be working with on the poster project (last name, too)? What topic will
you be presenting? Please be as specific as you can.
2. Match the appropriate distance unit for the distances shown:
Astronomical unit (AU)
Milky Way to Andromeda galaxy distance
Megaparsec (Mpc)
Earth to Saturn distance
Light year (ly)
Sun to Sirius distance
Kilometer (km)
North pole to equator distance
3. About what time of day would you expect to observe a first quarter Moon rising?
4. (1 point) If the Sun appears in the middle of a Zodiacal constellation right now, in
one solar day, most likely:
a. The Sun will still be in the same Zodiacal constellation
b. The Sun will be slightly west in the same Zodiacal constellation
c. The Sun will be in a different Zodiacal constellation
d. The Sun will be slightly east in the same Zodiacal constellation
5. At noon, shadows cast by objects are shortest at:
a. vernal equinox
b. summer solstice c. autumnal equinox
d. winter solstice
Earth reaches its perihelion point closest to:
a. vernal equinox
b. summer solstice c. autumnal equinox
d. winter solstice
6. Which of these particles is a component of an atomic nucleus? There may be more
than one right answer, so circle all that are correct.
a. proton
b. electron
c. neutrino
d. photon
Which of these particles has an electrical charge? There may be more than one right
answer, so circle all that are correct.
a. proton
b. electron
c. neutrino
d. photon
7. (3 points) Explain, for each of the equations below, what the variable on the left
stands for.
€
€
s = 0.0174 r α °
s is the _____________________________ of an object
P2 = a3
P is the _____________________________ of an object
#2
1&
v2 = G m % − (
$r
a'
v is the _____________________________ of an object
8. In the picture of the rocket below, the arrow already drawn is showing the “action”
force on the rocket. Draw:
a. an arrow showing Newton’s third law reaction force
b. an arrow showing how another outside force must be pushing
on the rocket (hint: notice that the path of the rocket seems to
be curved).
9. (1 point) Tides are controlled by:
a. The Washington State Department of Natural Resources
b. The centifugal force in the Earth’s orbit
c. Only the gravitational force of the Moon
d. The gravitational and centripetal force difference acting on the Earth
10. (3 points) Match the capital letter concept to the correct small letter example
illustrating the concept.
X. Conservation of angular momentum
Y. Kepler’s second law
Z. Conservation of energy
x. A planet travels slowest at aphelion.
y. Almost all bodies in the solar system revolve in a counterclockwise direction around
the Sun.
z. A spacecraft can gain velocity by doing a “slingshot” orbit around a planet, which
slows down the planet in its orbit by a tiny amount.
Essay questions — choose three of the five questions; circle the numbers of the ones
chosen, so I know which ones to grade. Please answer each question in
sentence/paragraph format or a drawing, depending on what is asked.
11. In the delightful movie Wallace and Gromit: The Curse of the Were-Rabbit,
astronomy plays a major role:
• the full moon appears in the sky four consecutive nights in a row.
• on one of those nights, the full moon appears about 45° above the horizon as the sun sets.
For each of these points, explain if it is scientifically accurate or not, and, if not,
how Aardman Studios (the producer of the film) should have fixed it.
12. On the TV show Eureka, the surface of Titan was depicted as having “snow”storms
made of solid ethane chunks. Ethane has the chemical formula C2H6. Explain whether
you believe ethane is polar or non-polar, and therefore whether ethane will be solid
or gaseous on Titan (the surface temperature of Titan is 94 K). As evidence, draw a
molecule of ethane, using the bonding rules from Exercise 1. Your answer need not be a
work of art, but should clearly identify the individual atoms and show what is bonded to
what.
13. Using Newton’s law of gravitation, explain what would happen to the orbital
period of the Earth’s orbit around the Sun if:
• The Sun shrank into a white dwarf but did not lose any mass
• The Earth stayed the same radius but doubled in mass
Note that no math is needed, but you should clearly state how Newton’s law can be
applied to these situations. Hint: in any case, nothing dramatic will occur – the orbital
period can only get longer, shorter or stay the same – you’ve simply got to pick and
justify the correct one.
14. You are an explorer in a spacecraft and arrive at a new solar system. You find a
potentially habitable planet and want to land on it, but you also want to make sure you
have enough fuel to leave the planet afterwards, so you need to find out the mass of the
planet. Suggest a simple measurement you can make while in orbit around the
planet, and how that and other information will help you determine the mass of the
planet.
15. Can you really see a star as a round object through a telescope? Do this calculation:
Determine the angular size α in degrees of Alpha Centauri, one of the closest large
stars to the Sun, using the “narrow triangle” approximation formula. Alpha Centauri has
a diameter of 1.7 × 106 km; its distance from us is 4.1 × 1013 km. Then answer the
question, given that even a good telescope can only see roundness in an object if it is 0.5
arc-seconds or larger.