A very loud train whistle has an acoustic power output of 100 W. If the sound energy spreads out spherically, what is the intensity level in dB at a distance of 89.0 meters from the train? (I0 = 10?12 W/m2)
a. 20.7 dB
b. 70.0 dB
c. 90.0 dB
d. 95.0 dB
e. 207 dB
c
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The fact that nearly all galaxies are moving away from us, with more distant ones moving faster, helped us to conclude that:
a. The universe is expanding. b. Galaxies repel each other like magnets. c. Our galaxy lies near the center of the universe.
A tightrope walker more easily balances on a tight wire if her pole
A) is held high. B) droops. C) is short but heavy.
When we say that jovian planets contain significant amounts of hydrogen compounds, we mean all the following chemicals except ________
A) water B) carbon dioxide C) ammonia D) methane
Which of these things is NOT a model in the sense used in the textbook?
a. Someone who is employed to appear in advertisements of merchandise. b. A guess about the contents of a box based on the weight of the box and the sounds it makes when shaken. c. A mathematical equation describing an observation of an unknown process. d. An analogy to a known process or object. e. A theory of what your cousin might have put in a box she sent you for your birthday.