Question

Two identical care moving in one direction honk each other at a frequency 1000 Hz. speed of one car is 80 k/h which speed of the other car is 60 km/h. Find frequencies at which the sound is heard by the drives of the cars. Find intensity sound when the distance between cars is 300 m. Assume that horns of both cars have power 400 W.

Answer 1

What do you mean by "moving in one direction"

are they right behind each other ???

are they moving in the same direction or moving towards each other ???

Here you need to use Doppler shift formula.

If cars are moving towards each other, then you can use

f' = (v + v_o) f / (v - v_s)

where v is speed of source car,

v_s is speed of sound

v_o is speed of observer car

f is frequency = 1000 Hz

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To find the intensity

we know

Intensity = power / area

here area = 4*pi*r²

so,

Intensity = power / 4*pi*r²

Intensity = 400 / 4*pi*300²

Intensity = 3.54e-4 W/m²