Submarine Distance - Hard Doppler effect

In summary: I had a completely different assumption in my head than the one I was using (I was using the one for water).Thanks for your help.I'll have a look at the link. I'm going to submit this assignment now.Thanks again for your help.In summary, the conversation is discussing a physics problem involving two submarines moving towards each other in still water. The French submarine is moving at 50.0 km/hr and sends out a sonar signal at 1100.0 Hz. The frequency detected by the French submarine from the reflected signal is 1222 Hz. The goal is to determine the speed of the U.S. submarine towards the French submarine, assuming a sound velocity of 1500 m
  • #1
pat666
709
0

Homework Statement



A French and a U.S. submarine are moving directly towards each other during manoeuvres in still water. The French submarine is moving at 50.0 km.hr-1. It sends out a sonar signal at 1100.0 Hz. The frequency detected by the French submarine (reflected back from the U.S. submarine) is 1222 Hz. How fast is the U.S. submarine traveling towards the French submarine? Assume the velocity of sound in sea water is 1500 ms-1.

Homework Equations





The Attempt at a Solution


Im thinking that the us submarine becomes a "virtual source" and that i have to solve this in two parts? I need some help getting started(and finishing probably). Thanks to any helpers.
 
Physics news on Phys.org
  • #2
I am stumped on this as well...

towards the us sub I have

f = (1500 +Vus / 1500 - 50) x 1100

Then back to french I have

1222 = (1500 +50 / 1500 - Vus) f

But I assume this is incorrect because when I sub the first into the second Vus cancels out...
 
  • #3
1ST put your velocuty into m/s (frequency is in hz) then 1222 = (1500 +50 / 1500 - Vus)*1500 +Vus / 1500 - 50) x 1100 (v_us doesn't cancel)
Thats what i did and everybody at uni i talked to... should come out at about 65ish
 
  • #4
cool, thanks Pat666
 
  • #5
that formula you used is the one out of the textbook for both the source and observer moving isn't it??
 
  • #6
yeah I subed the first eq (above post) into second but didn't change km/hr to m/s and made a mathematical error when working it out.
 
  • #7
what did you end up getting for the speed
 
  • #8
just doing it now but be buggered if I can figure it out! keep getting 0.33km/hr or 0.0905m/s
 
  • #9
did you get up to here the same??
 

Attachments

  • PF.png
    PF.png
    3.4 KB · Views: 543
  • #10
:redface: completely missed a step

I have been doing this assignment all weekend + all friday... I think my brain is officially fried!

Thank goodness this is my last question

How have you been finding it all? You seem to have a fairly good grasp. Are you on campus?
 
  • #11
yeah group A for eneg skills... you get around 65m/s.... Have you done the rest of the questions? I am not sure on my answer for the buoyancy 1.
My answers:
1)-.892C and an overflow of 0.7cm^3
2)941Hz and 938Hz and obviously 65m/s for sub
3)D of 15.6cm and height of 2.2m when the diametre is doubled
4)150m/s , 1.8*10^8 Nm^2 , Y=1.8*10^9Pa
5)open 139,278,417Hz and closed 69.7,209.1,348.6Hz and for b) 20 or 30Hz
6)4.389*10^7 n/m^2
7) went through on different thread same answer as you
8)2592grams
9)a) 2157.89kg/m^3 b) D 4.7kg and A 2.8kg

you disagree with any of these??
 
  • #12
I finally get 65m/s :cry: because I am soooo happy!

Only differences are:

5. a) (i) 1st Harm. 7.32Hz 2nd Harm. 14.6Hz 3rd Harm. 22Hz
(ii) F1 = 3.66Hz ; f3 = 11Hz f5 = 18.3Hz

9. a) 1237kg/m^3
b) D reads Mblock = 8.2kg E reads Mfluid + Mbeaker = 2.8kg
 
  • #13
Im pretty sure your Q 5 is wrong and i think my Q 9 is wrong.
 
  • #14
I though Q5 was asking for individual frequencies of the first 3 harmonics (i) open and (ii) closed

I used for open f1 = v/2L f2 = 2f1 f3 = 3f1 and closed f1 = v/4L f3 = 3f1 f5 = 5f1
 
  • #15
Q5)

Since the pipe is open at both ends all harmonics are present
f_1 =v/2L=343/(2*1.23) since lambda is half of the pipe length
f_2=2f_1=278Hz
f3=3f_1=417Hz
closed
In this case only odd harmonics are present
f_1=v/4L=69.7Hz
f3=3f_1=209.1Hz
f5=5f1=348.6HZ

half your answers arnt audible <12Hz

Can you show me how you did Q9 pls
 
  • #16
what you said in your last post is true but you must have screwed up your calculations - what did you use for sound velocity ( that shouldve been an assumption that it is still 343 m/s)
 
  • #17
Ah... was 343 your assumption? I used a different value.

Q9.

Mblock - Mdisplaced fluid - D = 0

Mblock = 4.7 + 3.5 = 8.2kg

Or

D + E = Mbeaker + M liquid + Mblock

11 = 1 + 1.8 + Mblock

Mblock = 11 - 2.8 = 8.2kg
 
  • #19
Do your term 1 classes come up in cqucentral i can't get any of my cover sheets for my portfolio or physics assignment.
 
  • #20
No it's only showing term 2?
 
  • #21
yah I fured it out there's a tab that says "other academic" click on it and go to assignments and there all there... ps did you end up changing your sound velocity assumption?
 
  • #22
hehehe yep :blushing:
 

FAQ: Submarine Distance - Hard Doppler effect

1. What is the Hard Doppler effect in the context of submarine distance?

The Hard Doppler effect is a phenomenon that occurs when a submarine emits a sound wave and it is reflected by a stationary object, such as the seafloor or a submerged object. This causes a shift in the frequency of the sound wave, resulting in a change in perceived distance between the submarine and the object.

2. How does the Hard Doppler effect affect the accuracy of measuring submarine distance?

The Hard Doppler effect can significantly affect the accuracy of measuring submarine distance, as the perceived distance may be different from the actual distance due to the shift in frequency. This can be particularly challenging in underwater environments where sound waves can be distorted by various factors, such as temperature, salinity, and pressure.

3. What factors can influence the Hard Doppler effect in submarine distance measurement?

The Hard Doppler effect can be influenced by various factors, including the speed of the submarine, the angle of the sound wave, the composition of the water, and the presence of other objects or marine life in the area. These factors can impact the frequency of the sound wave and therefore affect the perceived distance between the submarine and the object.

4. How do scientists account for the Hard Doppler effect when measuring submarine distance?

To account for the Hard Doppler effect, scientists use advanced sonar technology that can accurately measure the frequency shift and calculate the actual distance between the submarine and the object. They also take into consideration other factors that may influence the sound wave, such as water temperature and salinity, to improve the accuracy of their measurements.

5. Are there any real-world applications for understanding the Hard Doppler effect in submarine distance measurement?

Understanding the Hard Doppler effect is crucial for various real-world applications, such as marine navigation, underwater communication, and military operations. By accurately measuring submarine distance, scientists and engineers can improve the safety and efficiency of these activities, as well as gain a better understanding of the underwater environment.

Similar threads

Doppler effect of submarines question. Please help
Replies
7
Views
7K
Submarine sonar doppler problem
Replies
1
Views
5K
Calculating Velocity and Direction Using the Doppler Effect
Replies
1
Views
2K
Doppler Effect Submarine Problem
Replies
30
Views
13K
How Does the Doppler Effect Calculate Submarine Depth and Velocity?
Replies
2
Views
4K
Kinematics Question Involving Submarine
Replies
2
Views
4K
Spring and Microphone (Doppler Effect...?)
Replies
7
Views
2K
Doppler Effect: Velocity of a train
Replies
4
Views
2K
Calculating frequencies with the Doppler Effect
Replies
1
Views
3K
Speed aircraft carrier based on reflected pulse frequency
Replies
2
Views
5K

Hot Threads

Recent Insights

Back
Top