Sonar is used to determine the speed of an object. The object is moving at 8.4146 m/s.
The frequency of any wave is defined as the number of cycles per second.
The frequency of the sound received is
f' = f x [(V+Vo /V-Vo)]
where f = 40kHz, f' = 42kHz, V =345 m/s, then the velocity of the observer will be
(V+Vo /V-Vo) = 42/40 =1.05
On rearranging the doppler shift formula, we have
Vo = 0.05 x 345 /2.05
Vo = 8.4146 m/s.
Thus, the object is moving at 8.4146 m/s.
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