Vs = (Fs + Fo / Fs - Fo) * V

  • Thread starter BuBbLeS01
  • Start date
In summary, the conversation was about calculating the speed of an approaching vehicle based on the frequency of a honking car horn. The proper frequency was given as 310.00 Hz and the observed frequency was measured at 342 Hz. The speed of sound in air was also given as 340 m/s. The formula to calculate the speed of the approaching vehicle is Vs = (Fs - Fo / Fs + Fo) * V, where Vs is the speed of the vehicle, Fs is the source frequency, Fo is the observed frequency, and V is the speed of sound. However, the formula only works if the object is moving away from the observer. If the object is approaching the observer, a different formula is needed.
  • #1
BuBbLeS01
602
0
Test tomorrow...please help!

Homework Statement


A student in a parked car honks the horn, which has a `proper' frequency of 310.00 Hz. An observer in an approaching vehicle measures the frequency of the sound to be 342 Hz. Calculate the speed of the approaching vehicle. Use 340 m/s as the speed of sound in air.


Homework Equations





The Attempt at a Solution


Fs = 310 Hz
Fo = 342 Hz
Vo = 0 m/s
V = 340 m/s
Vs = ?

I know
Vs = (Fs - Fo / Fs + Fo) * V
if the object is going away from the observer
but how I do calculate if the object is approaching the person?
 
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  • #2
You already have a thread open on this same question. Use it.
 
  • #3


To calculate the speed of the approaching vehicle, we can use the equation Vs = (Fs + Fo / Fs - Fo) * V, where Vs is the speed of the approaching vehicle, Fs is the frequency of the sound emitted by the horn, Fo is the measured frequency of the sound by the observer, and V is the speed of sound in air. In this case, since the observer measures a higher frequency (342 Hz) than the actual frequency of the horn (310 Hz), we can assume that the vehicle is approaching the observer. Therefore, we can use the equation as is and plug in the given values:

Vs = (310 Hz + 342 Hz / 310 Hz - 342 Hz) * 340 m/s
Vs = (-32 Hz / -32 Hz) * 340 m/s
Vs = 340 m/s

Therefore, the speed of the approaching vehicle is 340 m/s. Please note that the negative sign on the frequency difference cancels out, as we are only concerned with the magnitude of the difference. I hope this helps with your test tomorrow. Good luck!
 

1. What does the equation Vs = (Fs + Fo / Fs - Fo) * V represent?

The equation represents the relationship between the source frequency (Fs), observed frequency (Fo), and the speed of the waves (V) in a medium. It is used to calculate the velocity of a moving object or wave.

2. How do you calculate the observed frequency (Fo) in this equation?

The observed frequency (Fo) can be calculated by dividing the product of the source frequency (Fs) and the velocity (V) by the sum of the source frequency and the velocity. This can be written as Fo = (Fs * V) / (Fs + V).

3. Can this equation be used to calculate the velocity of any type of wave?

Yes, this equation can be used to calculate the velocity of any type of wave, as long as the source frequency (Fs) and observed frequency (Fo) are known. It is commonly used in physics, acoustics, and other fields of science.

4. How does the velocity of the wave affect the observed frequency?

The velocity of the wave directly affects the observed frequency. As the velocity increases, the observed frequency also increases. This means that if the wave is traveling faster, it will have a higher observed frequency.

5. Can this equation be used to calculate the velocity of sound in air?

Yes, this equation can be used to calculate the velocity of sound in air. In this case, the source frequency (Fs) would be the frequency of the sound wave, and the observed frequency (Fo) would be the frequency heard by an observer. The velocity (V) would represent the speed of sound in air, which is approximately 343 meters per second at room temperature.

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