Why does the intensity of waves from a small source decrease with the square of the distance from the source?
A) The waves run out of energy as they travel.
B) The waves spread out as they travel.
C) The medium through which the waves travel absorbs the energy of the waves.
D) The waves slow down as they travel away from the source.
E) The frequency of the waves decreases as they get farther from the source.
B
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Phase Angles: The phase angle of a series RL ac circuit with a 20.0-mH inductor and a certain resistor at 1000 Hz is 20.0°. What is the resistance in this circuit?
A. 145 ? B. 100 ? C. 245 ? D. 200 ? E. 345 ?
An ideal Carnot engine operates between reservoirs having temperatures of 125°C and -20°C. Each cycle the heat expelled by this engine is used to melt 30.0 g of ice at 0.00°C
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A helium balloon rises because of
a. Archimedes' principle. b. Pascal's principle. c. Bernoulli's principle. d. Torricelli's principle. e. none of these principles.
A child has a temperature of 101°F. If her total cross-sectional area is 2 m2, find the energy lost each second (in W) due to radiation, assuming the emissivity is 1 . (Assume the room temperature is 70°F.)
a. 217 b. 180 c. 90 d. 68 e. 850