Question

An observer is standing next to the tracks, watching a train approach. The train travels at 30 m/s and blows its whistle at 8,000 Hz as it approaches and then passes by the observer without slowing down. Assuming the speed of sound is 340 m/s, how much of a frequency change did the observer hear?

Answer 1

Answer:

The frequency heard by the observer will be "7351.35 Hz".

Explanation:

The given values are:

Source,

$V_s=30 \ m/s$

Frequency of source,

$F_s=8000 \ Hz$

Speed of sound,

$C=340 \ m/s$

As we know,

⇒  $F=(\frac{C+V_r}{C+V_s} )F_s$

Here,

$V_r=0$

So that the formula will be:

⇒  $F=(\frac{C}{C+V_s} )F_s$

        $=\frac{340}{340+30}\times 8000$

        $=7351.35 \ Hz$