1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Physics Echo Problem

  1. Feb 21, 2016 #1
    1. The problem statement, all variables and given/known data
    A boat is floating at rest in dense fog near a cliff. The captain sounds a horn at water level and the sound travels through the salt water (1470 m/s) and the air (340 m/s) simultaneously. The echo in the water takes 0.40s to return. How much additional time will it take the echo in the air to return?

    2. Relevant equations
    v = Δd/Δt

    3. The attempt at a solution
    First Attempt:
    v = Δd/Δt

    Δd = v Δt = (1470 m/s) (0.40 s) = 588 m

    Δt = Δd/v = 588m / 340 m/s = 1.73 s

    Δt = 1.73 s – 0.40 s = 1.33 s

    The echo in the air took 1.33 s longer to return.

    Second Attempt:
    I was thinking that 1.73 s would be the total time, so then I would have to divide 1.73 s by 2 to get the return time (0.865 s). Then I would subtract 0.40s from 0.865 s to get the additional time it took the echo to return, which would be 0.465 s. Like this:

    v = Δd/Δt

    Find total time:
    Δd = v Δt = (1470 m/s) (0.40 s) = 588 m

    Δt = Δd/v = 588m / 340 m/s = 1.73 s

    Then find return time:
    1.73 s/2 = 0.865 s
    Then find additional time:
    0.865 s - 0.40s = 0.465 s

    The echo in the air took 0.465 s longer to return.

    Please help me figure out which process is correct, if they even are correct :)

     
  2. jcsd
  3. Feb 21, 2016 #2
    pretty sure your 1st answer is correct. The question is not asking about the return journey, but total journey time - 0.4s in total for the underwater echo, so the question is looking for the difference in total time
     
  4. Feb 24, 2016 #3
    I am doing a similar qts
     
  5. Feb 24, 2016 #4
    Thanks so much for your help, mgkii :)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Physics Echo Problem
  1. Echo in the ocean (Replies: 2)

  2. The echo (Replies: 9)

  3. A physics problem. (Replies: 5)

  4. Echo problem ? (Replies: 1)

Loading...