Name _________________________________
PHYS 106
Homework 6
Fall 2015
Due: Thursday, 10 Dec 2015
When you do a calculation, show all your steps. Do not just give an answer.
You may work with others, but the work you submit should be your own. I expect numeric
answers to have a reasonable number of significant figures and correct units.
6.1 (a) Go to http://www.mesacc.edu/~kev2077220/flash/planet-density.html and follow the
directions to fill in the table below:
Note: my answers for “% Metal” and “% Rock” don’t quite match those given on the website.
Planet/Moon
Measured
Density
Calculated
Density
Q1. % Metal
% Rock
Earth
Venus
Mars
Mercury
Moon
(b1) What is the “Measured Density”?
(b2) Do you expect it to be larger or smaller than the actual density? Why?
(c) Question 2 (from website)
(1) Greatest difference between observed and uncompressed densities:
(2) Smallest difference between observed and uncompressed densities:
(3) Why do these densities differ more in one case than the other?
(4) Which terrestrial world would you expect to have the 2nd largest difference between
observed and uncompressed densities:
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(d1) Based on the chemistry of Earth and Moon rocks, it appears that both worlds formed at the
same distance from the Sun. Since they formed the same distance from the Sun, would we expect
the % rock and % metal to be
(Circle one.)
Hint: look at Q3.
about the same
very different
no way to know
(d2) Does your choice in (d1) match the values of the “measured (uncompressed) densities” in
your table above?
Yes
No
(Circle one.)
Why or why not?
(d3) What about the giant impact hypothesis explains why the uncompressed densities are so
different?
(e) Notice that Mercury has the highest uncompressed density. Why is this true for Mercury?
(f) Question 5 What 2 reasons do scientists have for using “only” rock and metal?
(1)
(2)
Write your answers to the following questions on a separate sheet of paper!
6.2 tides Bennett et al., ch. 4, p. 134, #13 (7th edn).
Include: how
6.3 How does the nebular/planetesimal theory of planet formation account for many of the
craters on solid surfaces of moons and planets in our solar system?
6.4 moon formation Bennett et al., ch. 8, p. 240, #12 (6th edn), p. 231, #12 (7th edn).
6.5 What processes cause the interiors of the terrestrial planets to be hot?
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6.6 On what plate of the crust are you located? Which way is it taking you?
6.7 (a) How do we know that the Earth has a liquid core?
(b) Why is the inner core solid even though it is hotter than the outer liquid core?
6.8 Jovian planets are significantly more massive than terrestrial planets, and they formed farther
from the sun than the terrestrial planets.
(a) Why were the jovian planets able to accumulate more solid mass than the terrestrial planets?
(b) What additional material(s) were these more massive protoplanets then able to add to their
masses?
6.9 Highway surfaces develop potholes over time.
(a) How can you use the number of potholes as an indication of the "age" of the paving?
(b) How is this similar to using craters to estimate the age of solid surfaces in our solar system?
(c) How is this different from using craters to estimate the age of solid surfaces in our solar
system?
6.10 (a) Mauna Loa is considered the "monarch of mountains." It is the largest volcano and the
largest single mountain of any kind on Earth. It is 97 kilometers (60 miles) long, 48 kilometers
(30 miles) wide, and rises about 8,742 meters (28,680 feet) from its base on the sea floor.
Calculate what fraction of the Earth's diameter the volcano is.
(b1) Use the information on p. 263, in Fig. 9.26 (6th ed) or p. 253, in Fig. 9.26 (7th ed), and
estimate the diameter of Olympus Mons on Mars.
(b2) Calculate what fraction of the diameter of Mars Olympus Mons is.
(c) Which planet has relatively larger volcanoes (based on your calculation -- Show your work.)?
(d) Mount Hood (shown in Fig. 9.11c, p. 253) is fairly tall and steep, but the Hawaiian islands
and Olympus Mons (http://quest.arc.nasa.gov/mars/teachers/tg/program2/xolympus.gif) are low
and shallow.
What makes the shapes of Mount Hood and Olympus Mons differ as described above?
6.11 Look at the images of the Hawaiian islands located at:
http://en.wikipedia.org/wiki/Image:Hawaiianislandchain_USGS.png
and look at this flash animation of Hawaii’s formation:
http://education.sdsc.edu/optiputer/flash/hotSpots.htm
(a) Why is there a chain of islands formed instead of a single island?
(b) What direction does the tectonic plate that Hawaii is on move? How do you know?
(c) Which Hawaiian island is oldest? How do you know?
(d) What about the animation is most unrealistic?
6.12 (a) List the four observed properties/features of our solar system that must be explained by
any theory of solar system formation.
(b) When we discover exoplanets, we find that their solar systems are not usually like ours. In
what major way do they often differ from our solar system?
6.13 Read sections 13.2-3, pp. 387-394 in the text (7th edn).
(a) What is a "hot Jupiter"?
(b) About how many extrasolar planets have been discovered? About how many have we
measured the size of? We must know the size to calculate the density!
(c) So do you believe our expectation that the massive exoplanets that are very near their stars
are made of material similar to Jupiter (instead of being rocky) is justified? Why or why not?
(d) How can we explain how these low density planets ended up in such a high temperature
region?
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