A sailor strikes the side of his ship just below the waterline. He hears the echo of the sound reflected from the ocean floor directly below 2.0 s later. How deep is the ocean at this point? Assume the speed of sound in sea water is 1560 m/s (Table 12–1) and does not vary significantly with depth.
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This is Giancoli Answers with Mr. Dychko. When the sailor strikes their bottom of the ship they're creating a sound wave that travels to the bottom of the ocean and then reflects back up to the ship. And so the time the sailor measures is the time to travel the depth of the ocean twice, the sound travels from the ship to the ocean bottom once and then goes back up, so, a total of 2 times. So, the amount of time to do one trip of this distance here equal to the depth is going to be half the time that the sailor measures. So, that'll be the speed of sound and water times t over 2 so, that's 1560 meters per second times 2 seconds divided by 2 which is 1. And that means we just round this number to 2 significant figures which is 1600 meters.
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