The two most abundant elements in Earth's crust are
A) silicates and carbonates.
B) silicon and oxygen.
C) oxygen and aluminum.
D) quartz and feldspar.
Answer: B
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The total mass of a binary system can be calculated from
a. the ratio of the angular separation from the center of mass of each of the stars. b. the distance to the binary and its radial velocity. c. the semimajor axis and period of the orbit. d. the radial velocities of the two stars. e. the time required for the smaller star to eclipse the larger star.
When a load is placed on the middle of a horizontal beam supported at each end, the top part of the beam undergoes
A) tension. B) compression. C) either of these D) none of these
It took two centuries for the Copernican model to replace the Ptolemaic model because:
A) in Copernicus' time, there were no telescopes. B) the Church wouldn't let anyone talk about Copernicus' model for 200 years. C) there was no scientific evidence to support either model until Galileo made his observations. D) the Ptolemaic model was simpler and more aesthetically pleasing. E) the Copernican model required complicated new terms to explain it correctly.
One ray that is useful in locating the image formed by a convex mirror is the ray that is incident on the mirror in a path directed toward the focal point. This ray is reflected
A. through the center of curvature. B. directly back along its incident path. C. on a path tangent to the mirror. D. on a path parallel to the mirror axis.