A trumpet player on a moving railroad flatcar moves toward a second trumpet player standing alongside the track both play a 490 Hz note. The sound waves heard by a stationary observer between the two players have a beat frequency of 2.0 beats/s. What is the flatcar's speed? Take the speed of sound to be 343 m/s.

Respuesta :

Answer:

The value is [tex]v_s = 1.394 \ m/s[/tex]

Explanation:

From the question we are told that

The frequency of the second player is [tex]f_2 = 490 \ Hz[/tex]

The beat frequency is [tex]f_b = 2.0 \ Hz[/tex]

The speed of sound is [tex]v_s = 343 \ m/s [/tex]

Generally the frequency of the note played by the first player is mathematically represented as

[tex]f_1 = f_2 + f_b[/tex]

=> [tex]f_1 = 490 + 2.0 [/tex]

=> [tex]f_1 = 492 Hz[/tex]

From the relation of Doppler Shift we have that

[tex]f_1 = \frac{ f_2 (v+ v_o )}{v-v_s }[/tex]

Here [tex] v_o\ is\ the\ velocity\ of\ the\ observer\ with\ value\ 0 \ m/s [/tex]

So

[tex]492 = \frac{ 490 (343+0 )}{343 -v_s }[/tex]

=> [tex]v_s = 1.394 \ m/s[/tex]