Name________________________
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219: Energy and the Environment
First Exam: March 7, 2013
You have 80 minutes to answer both portions of the test. The test is closed-book, opennote. You may use calculators, but not laptops or smartphones. Please put your name on
the top of ALL pages. Answer the questions in the spaces provided. You can go onto the
back if necessary.
1) (12 pts)
a) Show that the units for kinetic energy (1/2 mv2)
and gravitational energy (mgh) are the same.
b) A device called the GravityLight uses gravity to
power a small LED light. Suppose that you lift a 10
kg bag of sand 2 meters high. How much energy
have you given it?
c) If you can power a small LED light bulb (about
the brightness of a small candle) for 30 minutes,
what is the wattage of the bulb?
d) Why can’t you convert all of the gravitational
energy into light?
a)(3 pts) KE = (kg)(m/s)2 = kg-m2/s2
Grav. PE = (kg)(m/s2)(m) = kg-m2/s2
b)(3 pts) mgh = (10 kg)(10 m/s2)(2 m) = 200 J (or 196 J, if they use g=9.8)
c)(3 pts) W= J/time = 200/(30x60) = 0.11 W
d)(3 pts) There will be a loss of energy to heat, either in heat given off by the light bulb
or heat in the gears of the mechanism that lowers the sand bag
2) (5 pts) Suppose that you turn on a forced-air electric heating system in your house so
that you can stay warm, and that your electricity comes from a hydroelectric power plant.
Describe the sequence of energy and mass conversions involved with the process, start to
finish (the finish is you getting warm).
1)
2)
3)
4)
Nuclear fusion inside the sun (converting hydrogen to helium)
Solar radiation (sunlight) reaches Earth.
Sunlight evaporates water from ocean (converts water to vapor)
Sunlight warms atmosphere, causing convection the lifts water vapor to high
altitudes, gaining gravitational potential energy
5) Water vapor condenses to form rain.
6) Rain falls, converting gravitational potential energy to kinetic energy, first
through the air, then down through river and through hydroelectric dam.
7) Falling water moves turbine, generating electricity.
8) Electricity flows through wires to house, loses energy to heat in the heating coils.
9) Motor in heater pushes warm air through house.
10) Warm air molecules transfer heat to your skin.
Name________________________
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3) (8 pts) The figure to the right shows per
capita energy consumption (pcec) for
China, Europe, the FSU (Former Soviet
Union), USA, and World.
a) Identify the five curves.
b) Explain the shape of curve #4.
c) Explain the dip in the curves to the far
right.
d) Which of these curves has had the most
dramatic change over this time period?
Why? Why is it affecting curve #2?
a)(2 pts) China (1), Europe(3), the FSU(4), USA(5), and World(2)
b)(2 pts) The big drop is the collapse of the Soviet government and economy.
c)(2 pts) That is the global economic recession of 2009.
d)(2 pts) China, going from close to zero to about 80. China’s population is so large that
this is noticeably affecting the World curve.
4) (12 pts) The efficiency of an incandescent light bulb is typically about 5%.
a) What happens to the rest of the energy?
b) The textbook also describes that same light bulb as being 1.3% efficient. What do they
mean by that?
c) Suppose you take the energy from burning a gallon of gasoline to power a 100 W light
bulb. How long could you light the bulb?
d) Why can’t you answer (c) exactly? (i.e., what other information do you need to know?)
a) (2 pts) Lost to heat (the bulb gets hot).
b) (2 pts) The power plant that generated the electricity is generally only 30-35%
efficient, with most energy lost to heat at the plant. [they could also talk about loss of
heat along electric power lines]
c) (4 pts) 1 gal gas = 1.24 x 105 Btu x (1055 J/Btu) = 1.31 x 108 J
time = J/W = (1.31 x 108 J)/100W = 1.31 x 106 s (or 15.14 days) WITH NO ENERGY
LOSS
(2 pts) Answer should be about 1/3 of this because of the efficiency of the generation =
~ 4 x 105 s (or about 5 days)
d) (2 pts) You don’t know the efficiency of the generator that converts gas to electricity.
Name________________________
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5) (8 pts)
a) The equation for the rate of heat flow through a wall is Q/t = (A x ∆T)/R (where Q is
energy, t is time, A is area, ∆T is the difference between the change in temperature on the
inside and outside, and R is the insulation value). Explain how the heat loss of a building
depends on ∆T.
b) Use (a) to draw a graph of a typical St. Louis house’s heating+cooling cost over the
course of a year.
c) Explain or show how this would be different in Norway and in Costa Rica.
a) (2 pts) You lose more heat proportional to the difference in temperature between the
inside of your house and the outside.
b) (2 pts) The curve looks like a sine wave and has 2 peaks, at Jan and July.
c) (4 pts) Norway – the curve has one peak, at January.
Costa Rica – the curve has one peak, at July.
Name________________________
6) (10 pts) Examine the diagram of the
anticline on the right.
a) How did this anticline likely form?
b) What can you tell about the layer of
rock on top of the region that says
“Gas?”
c) Why are the water, oil, and gas
layered in this way?
d) How could you find this region of gas without having to drill into it?
e) Sometimes geologic folds like this are accompanied by faults from earthquakes. Why
might that be a bad idea (for finding oil and gas)?
2 pts each
a) Tectonic plate collision
b) It is impermeable (the gas and oil cannot easily pass through it)
c) By density (gas is lightest, then oil, then water)
d) Use seismic waves to make images of the layers.
e) The oil and gas can flow up the fault and escape out the surface.
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Name________________________
7) (8 pts) a) Ten years ago, Canada was
not even in the top 20 for the ranking of
oil reserves, by country. Now, Canada is
ranked 2nd, behind only Saudi Arabia, in
terms of oil reserves. Explain this from
an economic standpoint.
b) Describe what methane gas hydrates
are, and how they form in offshore
regions.
c) Use what you know about the
temperature/pressure stability region for
methane gas hydrates to explain how the
hydrates in offshore sediments would be
unstable and turn to methane gas if the
sea level fell.
a) (2 pts) Canada’s reserves are in heavy, solid tar shales and oil sands, which were not
previously counted because they were not economically profitable to retrieve and
produce.
b) (3 pts) Methane frozen with water ice. They form from interaction of methane given
off by bacteria with water in the ocean sediments.
c) (3 pts) If the sea level fell, the pressure would drop, and this would make the methane
gas hydrates convert to liquid water and natural gas.
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Name________________________
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8) (6 pts) One of the challenges of
making decisions about energy policy is
balancing short-term vs. long-term
interests.
a) Examine the diagram to the right, and
describe one way that it might be good
in the short term but bad in the long
term.
b) Now describe one way that in might
be bad in the short term but good in the
long term.
a) (3 pts) [Several options here] One possilibity: Good for jobs, economy, lowers cost of
oil, industry, etc. Bad because we will use up our national resources quickly and then
become dependent upon foreign oil quicker.
b) (3 pts) One possibility: Bad – increases air pollution and global warming by
encouraging increased use of fossil fuels. Good – when US oil runs out quicker it will be
forced to move to more sustainable energy sources faster.
[Answers could also involve influences for increasing or decreasing the use of other
energy sources such as coal or nuclear]
9) (6 pts)
a) Why do anthracite deposits correlate with mountainous regions?
b) Coal forms on land from the accumulation of swamp material, but why is it often vital
for the formation of coal that there have been periods in Earth’s past where high sea
levels have flooded much of the land?
b) What are two different ways that the use of coal can cause increased stream
acidification?
2 pts each:
a) Need the high pressures from plate collisions to make the highly metamorphosed
anthracite.
b) You need to bury the swamp material to give it the pressures to turn it to coal, and
ocean sediments will do this.
c) Washing coal before combustion, or burning coal (which puts sulphur acids into the
atmosphere, which then rain out as acid rain).
Name________________________
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10) (8 pts) Much of
understanding the processes of
climate change involves
understanding the ways that
different Earth systems interact
with each other, often through
“feedbacks” that can amplify or
minimize a change to part of
one system. This diagram
shows a set of feedbacks that
would result from global
warming. Some amplify the
warming and some diminish it.
Pick four of the examples of
feedbacks and explain how
they operate to have either a
Warming or Cooling effect.
2 pts each (students pick any 4):
WARMING:
a) “Glacial Retreat decreases reflectivity of poles:” Ice reflects sunlight efficiently, so less ice means Earth
absorbs more solar energy and gets warmer, and melting more ice.
b) “Polar thawing speeds decay and release of carbon now held in permafrost:” Thawing of Arctic
permafrost causes frozen methane gas hydrates to melt, releasing methane into the atmosphere, which
increases the greenhouse effect and causes warming that increases the thawing.
c) “Faster temperature rise in high latitudes reduces temperature differential between equator and poles,
stalls ocean currents, and reduces pumping of CO2 to deep ocean:” the temperature rises causes a
slowdown of the thermohaline circulation of water through the oceans, which means that less CO2 goes
into the ocean, which means that more is in the atmosphere, which causes a larger greenhouse effect and
causes warming that increases the slowdown of thermohaline circulation.
d) “As oceans warm, their capacity to hold dissolved CO2 diminishes:” less CO2 in the ocean means more
in the atmosphere, which causes a larger greenhouse effect and causes warming that decreases the ability of
the ocean to absorb CO2.
e) “Temperature rise evaporates more water, raises humidity:” the increased humidity causes a larger
greenhouse effect and causes warming that raises humidity.
f) “Deforestation releases additional CO2:” the additional CO2 increases the greenhouse effect and causes
warming.
COOLING:
g) “Rising humidity leads to increased cloud cover:” which blocks out sunlight, causing a decrease in
temperature.
h) “Deforestation makes tropics more reflective, which means less sunlight is absorbed by the ground and
reradiated as infrared (which is absorbed by greenhouse gases), so atmosphere cools.
i) “Plants grow faster in high-CO2 atmosphere and absorb carbon:” which means that there is less CO2 in
the atmosphere, so the reduced greenhouse effect means a cooler atmosphere.
Name________________________
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11) (9 pts)
a) Only about half of the carbon dioxide that we have emitted through burning fossil fuels
is in the atmosphere. Where has the rest gone?
b) Give an example of a problem that has resulted from this.
c) Explain why it is the case that the last time there was this much carbon dioxide in the
atmosphere, global sea levels were about 75-100 feet higher than they are today.
d) How do changes in the amount of solar energy leaving the sun over short and longer
time scales affect temperatures on Earth?
a) (2 pts) The rest has gone, split about evenly, into plants (biomass) and the ocean.
b) (2 pts) Increased ocean acidification [could be other examples]
c) (2 pts) Increased greenhouse effect from increased carbon dioxide leads to warmer
global temperatures.
d) (3 pts) The 11-year solar cycle changes Earth’s temperatures slightly over this cycle;
There is a longer drift in solar output over centuries that was responsible for the Little Ice
Age and the Medival Warm Period.
Name________________________
12) (8 pts)
a) What is responsible for the
large-scale pattern seen in
this figure?
b) What has been unusual
about the last ten thousand
years, compared to previous
interglacial periods?
c) Why were sea levels
25,000 years ago about 400 ft
lower than today?
d) How might the French
Revolution have been
triggered by a geologic
event?
2 pts each:
a) Milankovitch cycles [or, Earth’s orbital parameters; or, shape or ellipticity of Earth’s
orbit]
b) Unusually constant temperatures.
c) Peak of last Ice Age, lots of glaciers on land, so less water in the ocean.
d) Volcanic activity in Iceland lowered temperatures in Europe and caused crop failures
and famines, leading to public unrest.
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Name________________________
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Table 3-4d, p. 91