A 2000 Hz siren and a civil defense official are both at rest with respect to the ground. What frequency does the official hear if the wind is blowing at 12 m/s (a) from source to official and (b) from official to source?

Respuesta :

Answer:

a)[tex]f_1 = 2070.6 Hz[/tex]

b)[tex]f_2 = 1929.4 Hz[/tex]

Explanation:

Apparent frequency of the siren is given as

[tex]f = \frac{v_{rel}}{\lambda}[/tex]

as we know that the wavelength will remain the same as it is having originally

sowe know

[tex]\lambda = \frac{340}{2000}[/tex]

[tex]\lambda = 0.17 m[/tex]

a) Now when wind is blowing from source to official

so we have

[tex]v_{rel} = 340 + 12 = 352 m/s[/tex]

so we have

[tex]f_1 = \frac{352}{0.17}[/tex]

[tex]f_1 = 2070.6 Hz[/tex]

b) Now when wind is from official to source

so we have

[tex]v_{rel} = 340 - 12 = 328 m/s[/tex]

so we have

[tex]f_2 = \frac{328}{0.17}[/tex]

[tex]f_2 = 1929.4 Hz[/tex]