ANSWERS TO “TEST YOUR KNOWLEDGE” ON PAGE 38 Answers:
1. The answer is choice “b” or “Individual plates of calcium carbonate formed by single-celled algae arranged in spherical shells.
Choice “a” refers to “conodonts”, whereas choice “c” describes “stromatolites.” The latter form as accretionary structures in shallow water by the trapping, attachment, and cementation of sedimentary grains by microorganisms.
2. The answer is choice “c” or “Stibnite.” Please see the table below: Mineral Name Chemical Formula Classification
Stibnite Rutile
Ilmentite
Sb2S3 TiO2
FeTiO3
Sulfide Oxide Oxide
Crystal Form Orthorhombic Tetragonal Tetragonal
Hardness 2.0
6.0-6.5 5.0-6.0
Specific Gravity 4.6
4.23 4.7-4.79
Antimony (Sb) is alloyed with lead (Pb) to increase its durability. Usage includes batteries, low-friction metals, cable sheathing, flame-proofing materials, paints, ceramics, enamels, glass, and pottery.
Both rutile and ilmenite are oxides of titanium (Ti). Titanium is as strong as steel but with a much lower density. Thus, it is an important alloying agent with other metals. Uses include aircraft, spacecraft, engines, and applications where strong, lightweight, temperature-resistant metal becomes important.
3. The answer is choice “b” or “Magnetism.”
A “gauss” is a unit of measurement of magnetic induction or magnetic flux density. 1 gauss = 1 maxwell cm-2 = 1 * 10-4 weber m-2 = 10-4 tesla. In gravity studies the “gal” is a unit of acceleration. 1 “gal” = 1 cm sec-2.
In radioactivity, the standard unit is the “becquerel.” 1 becquerel = 1 disintegration sec-1 = 2.70 * 10-11 curie.
Dilophosaurus statue. Photo by Robert Font.
4. The answer is choice “a” or “dilophosaurus.” This two-crested lizard measured about 23 feet in length and weighed about 880 pounds.
“Saltasaurus” was a sauropod that lived in the Late Cretaceous. It had a short neck and stubby limbs. It measured about 42 feet in length and weighed around 14,000 pounds.
“Anchisaurus” was small, long-necked saurischian dinosaur that lived in the Early Jurassic. It was about 7 to 13 feet long and weighed around 70 pounds.
5. The answer is choice “b” or “[Ie = 9.7 * 1037 kg m2]”.
The moment of inertia describes the tendency of a body to rotate or the tendency of a body to remain rotating once that it is already in rotation. Moment of inertia is always defined about an axis.
Consider a solid sphere of radius R and mass M. To calculate the moment of inertia about an axis running through its cen- ter, we must slice the sphere into a series of infinitesimally thin solid cylinders of radius r and thickness dx. We must then sum up all of these over the entire sphere.
For a solid cylinder, the moment of inertia I is: I = ½ MR2
For the solid sphere: dI = ½ r2 dM
(1) (2)
2) times its thickness (dx). Thus:
2dx
Substituting (4) into (3): 2dx
(4) (5)
40 TPG •
Oct.Nov.Dec 2022
www.aipg.org
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