Question

As you are standing on the pavement, a car approaches you at a speed of 98 km/h, sounding its horn at a frequency of 9,213 Hz. Determine the frequency of the sound that you hear in SI units (Hz)

Answer 1

Given that a car approaches you at a speed of 98km/h or 27.22m/sec , sounding its horn at a frequency of 9213 Hz.

Let the car be the source and you are the observer then the frequency of sound that the observer hear is given by using the Doppler effect. This effect determine the change in frequency due to relative motion of source and observer.

So the frequency of sound that observer hear is given by

F(observer)=F(source)*(v/(v-u))

Where F(source)=frequency of sound from the source

v=speed of sound=343m/sec

u=speed of car/source

So, F(observer)=9213*(343/(343-27.22))

F(observer)=3160059/315.78

F(observer)=10007.15 Hz