ANSWERS TO QUESTIONS ON PAGE 29 Answers:
1. The answer is choice “c” or “MH” describes a “silt of high compressibility.” Clays of low plasticity are described as “CL.” Well-graded sands are classified as “SW.”
2. The answer is choice “a” or “lignite.”
“Lignite” or brownish-black coal is the lowest rank of coal (above “peat”). “Lignite” is mainly used as fuel for electric power generation.
“Subbituminous coal” and “bituminous coal” (depending on the ranks) have heating values ranging from about 8,000 to 14,000 BTU per pound. These are utilized as fuel in steam-electric power generation, for heat and power applications in manufacturing and in the development of “coke” fuel.
“Anthracite” has heating values around 14,000 BTU per pound. “Anthracite” coal depicts the highest rank of coal. It is used in residential and commercial heating.
Because of environmental concerns, sulfur content has become as important as the BTU values for coal. Low sulfur content is obviously most desirable.
. 3. The answer is choice “b” or “”Pyrolusite” (MnO2).
“Rhodocrosite” is also an ore of manganese, but constitutes manganese carbonate (MnCO3). “Sphalerite” is a sulfide and a main ore of zinc (ZnS).
4. The answer is choice “b” or “Lias.” “Malm” is the youngest of these three “epochs.” 5. The answer is choice “a” or “( and are parallel to each other).” The proof follows:
We can test these using vector mathematics. We know that for two non-zero vectors, the “dot product” is zero when they are perpendicular to one another. Similarly, for two non-zero vectors, the “cross product” is zero when they are parallel to each other.
Calculating the “dot product” first: = 3 i 2 k = 6 i 4 2 k
= g1y1 g2y2 g3y3 = (3 * 6) (2 * 4) (1 * 2) = 28
(1) (2) (3) (4)
Since the value 0 in (4), then the vectors are not perpendicular to each other! Calculating the “cross product” next: = 3 i 2 k = 6 i 4 2 k = X
(1) (2) (5)
Let be the magnitude of . Then: = [( ) * ( ) - ( )2]1/2
(6)
= [(3 * 3) (2 * 2) (1 * 1)] * [(6 * 6) (4 * 4) (2 * 2)] – [( 3 * 6) (2 * 4) (1 * 2)]2}1/2 Thus, the magnitude of X = is: = (14 * 56 – 784)1/2 = 0
(7) From the result calculated in (7), we see that and are parallel vectors!
This math is easy stuff, isn’t it? Well, maybe not, but it is certainly a tool for us to use to solve geologically-related prob- lems! C’est la vie, mes amis!
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