Question 18: Waves

Question

Two cars approach a stationary observer from opposite sides as shown in the figure.
The observer hears no beats. If the frequency of the horn of the car B is 504 Hz, then the frequency of the horn of the car A will be
![](https://app-content.cdn.examgoal.net/fly/@width/image/1lbwqkryr/3f9c88b5-8c7e-4ea4-aec4-5d529c78262a/030cee30-80ad-11ed-a639-815a61f5001e/file-1lbwqkrys.png?format=png)

Accepted Answer

Apparent frequency of car A = Apparent frequency of car B
$ \Rightarrow {v \over {v - {v_s}}} 	imes 
u  = {v \over {v - v{'_s}}} 	imes 
u '$
$ \Rightarrow {
u  \over {v - 15}} = {{504} \over {v - 30}}$
$ \Rightarrow 
u  = {{340 - 15} \over {340 - 30}} 	imes 504$ [$\because$ velocity of sound in air is 340 m/s]
$ \Rightarrow 
u  = 529.2$ Hz

Answer

529.2 Hz

Answer

440.5 Hz

Answer

295.2 Hz

Answer

None of these

Waves

Two cars approach a stationary observer from opposite sides as shown in the figure. The observer hears no beats. If the frequency of the horn of the car B is 504 Hz, then the frequency of the horn of the car A will be

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