Why does the useful resolving power of a ground-based telescope not match its theoretical value?
A. The atmosphere blurs the image, decreasing the resolving power.
B. Mirrors can't be built accurately enough.
C. Mirrors cannot collect enough light to reach their theoretical expectations.
D. The theoretical value can only be reached when there is a Full Moon.
Answer: A
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The sidereal drive of a telescope mounting must turn the telescope
a. southward about the polar axis. b. eastward about the polar axis. c. westward about the polar axis. d. northward about the polar axis. e. none of the above
A steel rod (Es 5 210 GPa, dr 5 12 mm, ctes 5 12 3 1026/°C) is held stress-free between rigid walls by a clevis and pin (dp 5 15 mm) assembly at each end. If the allowable shear stress in the pin is 45 MPa and the allowable normal stress in the rod is 70 MPa, the maximum permissible temperature drop DT is approximately:
(A) 14 8C
(B) 20 8C
(C) 28 8C
(D) 40 8C
A given net force propels an object along a straight-line path. If the net force were doubled, its acceleration would
A) quadruple. B) double. C) stay the same. D) be half. E) none of the above
The metamorphic property of flat or elongated mineral grains in parallel layers is called
A) schist. B) cleavage. C) foliation. D) lithification.