What produces the 21-cm line that we use to map out the Milky Way Galaxy?
A) atomic hydrogen
B) ionized hydrogen
C) molecular hydrogen
D) carbon monoxide
E) helium
A) atomic hydrogen
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The highest frequency visible light is
a. violet. b. red. c. blue. d. green. e. yellow.
The ratio of the tensile fracture strength of ceramics to the compressive fracture strength is typically:
(a) 0.1 to 0.2 (b) 5 to 10 (c) 1 (d) 0.5
The following three appliances are connected to a 120-V house circuit: i) toaster, 1 325 W, ii) coffee pot, 650 W, and iii) microwave, 600 W. If all were operated at the same time, what total current would they draw?
a. 2.10 A b. 47.5 A c. 7.15 A d. 21.5 A e. 11.0 A
What does the word "normal" mean in the phrase "normal force"?
A) the force that is usually exerted by a surface B) the total force exerted by a surface C) the component of the force exerted by a surface parallel to the surface D) the component of the force exerted by a surface perpendicular to the surface E) the force is due to contact between two objects.