A stationary railroad whistle is sounded. An echo is heard 5.0 seconds later by the train's engineer. If the
speed of sound is 343 m/s, how far away is the reflecting surface?
A. 68 m
B. 140 m
C. 860 m
D. 1700 m
E. 2000 m
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The speed of sound is 343 m/s and the time it takes for the sound to travel to the reflecting surface and back is 5.0 seconds.
The total distance traveled by the sound is the speed of sound multiplied by the time, which is 343 m/s * 5.0 s = 1715 m.
However, this is the total distance traveled by the sound, which includes the distance to the reflecting surface and the distance back. Since these two distances are the same, the distance to the reflecting surface is half of the total distance, which is 1715 m / 2 = 857.5 m.
So, the reflecting surface is approximately 860 m away. The answer is C. 860 m.
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