The polarity of the voltage in a circuit operating at 60 Hz reverses
A) 90 times per second.
B) 30 times per second.
C) 10? times per second.
D) 120 times per second.
E) 60 times per second.
D
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_________is the minimum distance between two points that can be observed.
Fill in the blank(s) with the appropriate word(s).
What kind of "spark" is the molecular cloud awaiting?
A: B, C, or D are possible B: cooling until the cloud cannot support itself C: a wind from a nearby massive star D: a pressure wave from a nearby supernova E: none of the above
The accelerations possible for a ball on an inclined plane
A) range from zero to g. B) range from g to infinity. C) have no limit.
At the Earth’s orbital distance, the intensity of the solar radiation is approximately 1400 
What is the value for the rms Electric field strength in solar radiation?
A. 726 V/m B. 363 kV/m C. 527 kV/m D. 513 kV/m