Solved: Physics: Using Sound to Measure Distance The

Chapter , Problem 1.4.97

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Physics: Using Sound to Measure Distance The distance to the surface of the water in a well can sometimes be found by dropping an object into the well and measuring the time elapsed until a sound is heard. If II is the time (measured in seconds) that it takes for the object to strike the water, then t1 will obey the equation s = 16ft, where s is the Vs distance (measured in feet). It follows that II = 4. Suppose that t 2 is the time that it takes for the sound of the impact to reach your ears. Because sound waves are known to travel at a speed of approximately 1100 feet per second, the time t 2 to travel the distance s will be s . t 11 . 2 = --. See the I ustratlOn. 1 100 Falling object: t = {S 1 "4 Sound waves: t2= IIO Now tl + tz is the total time that elapses from the moment that the object is dropped to the moment that a sound is heard. We have the equation . d Vs s Total time elapse = 4 + 1 1 00 Find the distance to the water's surface if the total time elapsed from dropping a rock to hearing it hit water is 4 seconds.