Solving a Physics Problem: Calculating Ambulance Speed with Sound Waves

In summary, the problem involves determining the speed of an ambulance based on the observed frequency of its siren before and after passing by a stationary observer. The Doppler equation is used, with the observed frequency (f') = 480 Hz, frequency (f) = 560 Hz, the velocity (v) = 343 m/s, the velocity of the observer (vo) = 0 m/s, and the velocity of the ambulance (vs) being solved for. The calculated velocity of the ambulance is 57.17 m/s, but the answer in the back of the book is given as 26.4 m/s. It is possible that there may be missing or incorrect information in the problem.
  • #1
pippermay
7
0
Hi,
Can someone please help me with the following problem:

Standing at a crosswalk, you hear a frequency of 560 Hz from the siren of an approaching ambulance. After the ambulance passes, the observed frequency of the siren is 480 Hz. Determine the ambulance's speed from these observations.
 
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  • #2
Have you done anything on this? What is the problem about, besides simply sound waves? That should help you to find an equation (or equations) you can use.
 
Last edited:
  • #3
I have placed the information in the Doppler equation "I quess that it what it is called." Where the observed frequency (f') = 480 Hz, frequency (f) = 560 Hz, the velocity (v) = 343 m/s, the velocity of the observer (vo) = 0 m/s, and I am solving for the velocity of the ambulance's speed (vs).

f' = ((v - Vo)/(v + vs))f

vs = ((f(v-vo))/f') - v
vs = ((560(343-0))/(480)) - 343
vs = 57.17 m/s

I get the velocity of the ambulance to be 57.17 m/s, but according to the back of the book the correct answer is 26.4 m/s. I just don't understand what I am doing incorrectly.
 
  • #4
You must have missed somethingi from the problem. 57.17 comes out correctly with the information you have given us. Maybe the equation is wrong?
 
  • #5
560 is not the actual frequency of the source at rest it is also the apperent frequency when the amb is coming towards the observer...
 
  • #6
I just wanted to say Thanks For helping me.
 

1. What are sound waves?

Sound waves are a form of energy that travel through a medium, such as air or water. They are created by vibrations or disturbances in the medium, which cause particles to compress and expand, creating a wave-like pattern.

2. How do sound waves travel?

Sound waves travel in a straight line from the source of the sound, in all directions. They can travel through different mediums, such as air, water, or solids, but the speed of the wave will depend on the properties of the medium.

3. What is the speed of sound?

The speed of sound depends on the medium it is traveling through. In dry air at room temperature, sound travels at approximately 343 meters per second. However, this speed can vary depending on factors such as temperature, humidity, and altitude.

4. How does frequency affect sound waves?

Frequency is the number of waves per second and is measured in Hertz (Hz). It determines the pitch of a sound, with higher frequencies producing higher-pitched sounds and lower frequencies producing lower-pitched sounds. The human ear can hear frequencies ranging from 20 Hz to 20,000 Hz.

5. How are sound waves measured?

Sound waves are measured in terms of amplitude and frequency. Amplitude is the maximum displacement of particles in the medium and is measured in decibels (dB). Frequency is measured in Hertz (Hz). Additionally, sound waves can also be described in terms of wavelength and speed.

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