Doppler effect when moving towards then past each other

In summary, the conversation discusses the situation of driving on a highway and hearing an emergency vehicle's siren approaching and passing by. The frequency of the siren changes from 2800 Hz to 2120 Hz as the vehicle passes by. With the speed of sound in air being 340.0 m/s, using the Doppler equation F2=F1(vsound/(vsound+/-vobject)), the speed of the emergency vehicle can be calculated.
  • #1
PHolloway27
1
0
You are driving along a highway at 27.50 m/s when you hear the siren of an emergency vehicle traveling in the opposite direction on the other side of the highway. When the vehicle is approaching you, you hear the frequency of the siren as 2800 Hz, but when it is past you the frequency becomes 2120 Hz. What is the speed of the emergency vehicle? The speed of sound in air is 340.0 m/s.
 
Physics news on Phys.org
  • #2
Welcome to PF!

Hi PHolloway27! Welcome to PF! :wink:

Show us what you've tried, and where you're stuck, and then we'll know how to help! :smile:
 
  • #3
Seems like classic doppler to me

F2=F1(vsound/(vsound+/-vobject)

+ recceding
- approaching

just plug in the right numbers
 

What is the Doppler effect?

The Doppler effect is the change in frequency of a wave when the source of the wave and the observer are in relative motion. This effect is commonly observed in sound waves, light waves, and other types of waves.

How does the Doppler effect occur when two objects are moving towards each other?

When two objects are moving towards each other, the frequency of the wave emitted by the source appears higher to the observer due to the compression of the waves. This causes a shift towards the higher end of the frequency spectrum, resulting in a higher perceived pitch or frequency.

How does the Doppler effect occur when two objects are moving past each other?

When two objects are moving past each other, the frequency of the wave emitted by the source appears lower to the observer due to the stretching of the waves. This causes a shift towards the lower end of the frequency spectrum, resulting in a lower perceived pitch or frequency.

What is the formula for calculating the Doppler effect?

The formula for calculating the Doppler effect is:
f' = f (v +/- vo) / (v +/- vs)
Where f' is the observed frequency, f is the emitted frequency, v is the speed of the wave, vo is the velocity of the observer, and vs is the velocity of the source.

How is the Doppler effect used in real life?

The Doppler effect is used in various applications in real life. It is used in weather radar to determine the speed and direction of moving storms, in medical ultrasound to measure blood flow and heart rate, and in astronomy to determine the velocity of stars and galaxies. It is also used in police radar guns to measure the speed of moving vehicles.

Similar threads

  • Classical Physics
Replies
13
Views
1K
Replies
1
Views
854
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Classical Physics
Replies
16
Views
933
  • Introductory Physics Homework Help
Replies
3
Views
2K
  • Advanced Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
2K
  • Introductory Physics Homework Help
Replies
1
Views
1K
Replies
3
Views
2K
Back
Top