Physics 1070 Second Hourly Exam November 24, 1999

Name:

This is a closed book exam. Be careful not to share your answers with anyone else, since the hallmark of science is honesty and integrity. Write all your answers carefully, completely, concisely, and legibly in the spaces provided on these exam sheets. Anything that can't be easily read and understood by the grader will be marked wrong. The 100 points for this exam will be worth 15% of your final grade.

1. True or False: Mark the following statement either true (T) or false (F) on the basis of the reading and discussions of this class. (30 points, 3 for each correct item).

F a) "Enrichment" increases the proportion of fertile nuclei in uranium over that normally found in nature. Enrichment increases the fraction of "fissile" nuclei.

T b) During the last century, the carbon dioxide concentration in the earth's atmosphere has increased.

F c) In a "linear dose theory" it is assumed that there is a minimum radiation dose below which no biological damage is done. In the linear theory, damage is proportional to dose all the way down to zero dose.

T d) The Chernobyl incident put more radioactive material into the earth's atmosphere than all nuclear weapons tests combined.

F e) Hydroelectric power, like nuclear power, is independent of the current energy from the sun. Water power gets its ulimate power from the sun.

F f) The wavelength of microwave radiation is less than that of ultraviolet since its energy is less. MW energy is less but its wavelenth greater than UV.

T g) Nuclear fission energy is dependent upon the fact that more fission neutrons are released than are absorbed, which is not necessary for nuclear fusion energy.

F h) The strong nuclear attractive force has a significant effect on the atomic electrons.The strong nuclear force is very short-ranged and doesn't extend out to the atomic electrons.

T i) The albedo of the earth would decrease if all of the polar ice caps melted. With less ice, there would be less overall reflectivity.

T j) Volcanic eruptions tend to lower temperatures of the earth's surface.The dust reflects solar energy, keeping it away from the earth.

2. Multiple choice: Pick the numbered item which best completes the statement (20 points, 4 for each correct item).

3 a) Coal power is less "environmentally friendly" than natural gas because?

1. There is less of it.

2. There is more of it.

3. It contains a greater percentage of carbon.

4. It contains a smaller percentage of carbon.

5. It burns at a higher temperature.

6. It requires cooling towers.

5 b) The cost of mining has gone up in recent times because?

1. Miner's wages have increased.

2. The cost of mining machinery has gone up.

3. Governments have discouraged mineral exploration.

4. The demand for metals has decreased.

5. More ore has to be dug to obtain the same amount of desired material.

6. Taxes on minerals have gone up.

2 c) M.K. Hubbert argues that the production history (amount produced) of an energy commodity such as oil is best described by a?

1. Logistic curve

2. Normal curve

3. Quadratic curve

4. Exponentially rising curve

5. Exponentially falling curve

6. Straight line

2 d) If the load factor of a given form of transportation doubles, the per capita energy cost of transportation by this method.

1. Is doubled

2. Is halved

3. Remains the same

4. Is quadrupled

5. Is cut in quarter

3. Matching: Choose the item in the column on the right that, on the basis of course readings and discussions most closely associates with the description on the left. (30 points; 3 for each correct matching) [Bonus: extra 5 points; define, in one or two sentences, any one of the items listed in the right hand column.]

17	a) Radiation exposure x quality factor	1) moderator
20	b) The result of solar energy of the distant past	2) fissile nuclei
10	c) The conversion of visible light from the sun into trapped infared radiation	3) microwave radiation 4) control rod
14	d) Electromagnetic energy of very high frequency	5) plate tectonics
16	e) The Rasmussen report	6) Hubbert method
18	f) High fossil fuel input farming	7) troposphere
9	g) The solar electromagnetic frequencies, which are least absorbed by the earth's atmosphere	8) stratosphere 9) atmospheric window
13	h) The nucleus of the common helium atom	10) greenhouse effect
1	i) Slows neutrons to enhance energy production by nuclear fission	11) albedo 12) isotope
8	j) The stable part of the earth's atmosphere	13) alpha particle 14) gamma radiation 15) nuclear fusion 16) event tree 17) rem 18) North American agriculture 19) swidden agriculture 20) fossil fuel

Extra credit definition:

4. Short essays: Answer any two of the following questions (20 points, 10 for each correct essay). In your answers, do not rely solely on your own opinions. Back them up with information obtained from the text and class discussions. (Bonus 10 points for complete answer to a third question.)

a) Defend or criticize the following statement: The world should emphasize nuclear power instead of relying upon fossil fuels. Both pose severe threats to our lives and our environment; we have a limeted amount of fossil fuels which will run out in the forseeable future whereas nuclear energy could take us thousands of years into the future.

b) Is it true that the best plan for the future of the world's agriculture is to concentrate on the fewest possible varieties of the most energy efficient plants? Explain your answer. Not a good plan since it would lead to a very unstable agricultural system - one plant disease or pest could then deprive most of humanity of its food supplies.

c) Explain the following statement: If it can be achieved, nuclear fusion power is a better answer to the world's energy needs than is nuclear fission power. Fusion power does not produce the large amount of radioactive waste that is charachteristic of fission power and there is potentially more of it available.

d) Explain the similarities and differences between "wind power" and hydroelectric power". Show how both are ultimately forms of "solar power". Both depend upon the sun; the wind arises from differently heated parts of the earth's surface due to the different solar intensity at different latitudes whereas water power depends upon different levels of the earth's surface, the sun evaporating water at sea-level (low) , dumping it as rain over the hills and mountains (high) from which it runs down, converting its gravitational potential energy into kinetic energy of moving rivers.

e) How is it possible to use the amount of oxygen found in the earth's atmosphere and crust to estimate the total amount of fossil fuel available? Criticize this estimate. If all of the atmospheric and crustal oxygen is a result of past photosynthesis, as is all of the fossil fuels, then there is a unique relation between the amounts of each, set by the well-understood chemistry. Measuring the amount of one tells you how much exists of the other. But suppose we can't measure all of the oxygen accurately - it may be buried deep underground or under the seas. Or, suppose that some of the fossil fuels are not the product of terrestial photosynthesis, e.g., were deposited in the earth at its creation.

f) Explain why urban areas are, or are not, warmer and have more pollutants, than their surrounding rural areas. Does the city environment influence that of local and distant rural areas? Dry city concrete has a lower heat capacity than moist soil and vegetation, hence rises to a higher temperature for a given amount of received solar energy; some of the solar energy falling on vegetation is turned into stored chemical energy via photosynthesis whereas all falling on concrete becomes heat meaning increased temperature; also, the tall urban buildings block cooling breezes. The concentration of people, vehicles, industry, and buildings, characteristic of urban areas, produces both more heat energy and mor pollutants than do rural areas. But pollution and heat don't stay still - they can be, and are, transported from the city to close and distant rural areas by wind an wqter flows.

g) Defend or criticize the statement: The mandatory introduction of catalytic converters for American automobiles was desirable for the efficiency of our transportation system and the well being of our environment. When initially introduced, catalytic onverters reduced the number of miles per gallon achievable by cars and trucks, e.g., the efficiency, even though it cut dopwn on some of the gaseous pollutants. The fuel had to be reformulated to protect the catalysts which reliminated other , metallic, pollutants. Later on, reductions in car weight and the introduction of computer monitored and controlled engines restored, and even improved upon, the previous transportation efficiencies.