Doppler effect wavelength from car

Click For Summary
SUMMARY

The discussion focuses on calculating the Doppler effect for a car traveling at 30 m/s with a siren frequency of 600 Hz and sound velocity in still air at 330 m/s. The wavelength of sound waves is determined to be 0.05 m when the car is stationary. For the moving car, the wavelength in front is calculated as 0.5 m and behind as 0.6 m using the equations Wavelength behind = (Vm + Us) / Fs and Wavelength in front = (Vm - Us) / Fs. The frequency of the sound heard by a stationary observer can be derived from these wavelengths using the formula V = F * λ.

PREREQUISITES
  • Understanding of the Doppler effect
  • Familiarity with sound wave properties
  • Knowledge of basic physics equations related to wave mechanics
  • Ability to manipulate equations involving frequency, wavelength, and velocity
NEXT STEPS
  • Learn how to apply the Doppler effect equations in various scenarios
  • Explore the impact of different velocities on sound frequency and wavelength
  • Study the relationship between frequency, wavelength, and sound speed in different mediums
  • Investigate real-world applications of the Doppler effect in fields like astronomy and radar technology
USEFUL FOR

Physics students, educators, and anyone interested in understanding sound wave behavior and the Doppler effect in practical applications.

matt_crouch
Messages
157
Reaction score
1

Homework Statement



A car is traveling at 30m/s in still air. the frequency of the siren on the car is 600hz. The velocity of sound in still air is 330 m/s. what is the wavelength of the sound waves

a)directly in front of the car
b)directly behind the car

What is the frequency of the sound heard by a stationary observer

c)directly in front of the car
d)directly behind the car

Homework Equations



FD=CD/Cs *Fs


The Attempt at a Solution



Im not really sure where to start if someone could point me in the right direction.

Cheers
 
Physics news on Phys.org
matt_crouch said:

Homework Statement



A car is traveling at 30m/s in still air. the frequency of the siren on the car is 600hz. The velocity of sound in still air is 330 m/s. what is the wavelength of the sound waves

a)directly in front of the car
b)directly behind the car

What is the frequency of the sound heard by a stationary observer

c)directly in front of the car
d)directly behind the car

Homework Equations



FD=CD/Cs *Fs


The Attempt at a Solution



Im not really sure where to start if someone could point me in the right direction.

Cheers

OK, let's kick this off. Can you first get the frequency of the doppler shifted sound wave? I think your equation above (though you haven't defined what each variable represents) should tell you that.
 
jamesmo said:
OK, let's kick this off. Can you first get the frequency of the doppler shifted sound wave? I think your equation above (though you haven't defined what each variable represents) should tell you that.

Also, write out how to get your C's.
 
well i can find the wavelength of the car but i think its only when its stationary I am not sure

If Cs of the source is 30 m/s an the frequency is 600 hz
then the wavelength is

0.05 m

but I am not so sure where to go from there.. if i have Cs and Fs how do i find what the wavelength in front and behind is
 
actually i think i have the answer.. i used an equation that was stated in my textbook..

Wavelength behind = (vm+us)/Fs

where Vm= velocity of sound in medium
Us= velocity of source


and it gets an answer of 0.6 m

and

wavelength infront = (vm-us)/Fs

given an answer of 0.5 m

and from here i can calculate the frequency of each wavelength from V= F*(Lambda)
 
matt_crouch said:
actually i think i have the answer.. i used an equation that was stated in my textbook..

Wavelength behind = (vm+us)/Fs

where Vm= velocity of sound in medium
Us= velocity of source


and it gets an answer of 0.6 m

and

wavelength infront = (vm-us)/Fs

given an answer of 0.5 m

and from here i can calculate the frequency of each wavelength from V= F*(Lambda)

Awesome! Have a good one.
 

Similar threads

Replies
8
Views
1K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
1
Views
1K
Replies
3
Views
8K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 5 ·
Replies
5
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K