Alice holds a small battery operated device used for tuning instruments that emi

Question

Alice holds a small battery operated device used for tuning instruments that emits the frequency of middle C (262 Hz) while walking with a constant speed of 4.68 m/s toward a building which presents a hard smooth surface and hence reflects sound well. (Use 343 m/s as the speed of sound in air.)

(a) Determine the beat frequency Alice observes between the device and its echo. (Enter your answer to at least 1 decimal place.)

Hz
(b) Determine how fast Alice must walk away from the building in order to observe a beat frequency of 8.79 Hz.
m/s

Explanation / Answer

(a)frequency of echo received = 262(343 + 4.68)/(345- 4.68)
beat frequency = echo frequency - orignal(262 hz)

(b)frequency of echo received = 262(343 - v) /(343+v)
beat frequency = echo frequency - orignal(262 hz) = 6
equate to find v

note : ive taken velocity of sound as 343 m/s

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