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Pulse Question

  1. Jan 30, 2016 #1
    1. The problem statement, all variables and given/known data

    54a9cd5f702fff5fd1b3f88622813723.png
    2. Relevant equations
    Refer to 3.

    3. The attempt at a solution
    My problem is the theory I am unsure how any equations apply to this problem. This seems bad that I have no attempt at solution but I am honestly unsure how to start or of any relevant equations.
     
  2. jcsd
  3. Jan 31, 2016 #2

    ehild

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    Think instead of looking after equations. Imagine, you stand at distance d from a wall, and you clap once. The sound reflects from the wall. What time after the clap does the echo reach you?
     
  4. Jan 31, 2016 #3
    v=dt
    so t = v/2d
     
  5. Jan 31, 2016 #4

    ehild

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    You mean the time is the shorter the longer is the distance ???
    What is the correct answer?
    And what is the time if the wall is at distance d+w?
    What is the difference of times if one wall is at distance d and the other wall is w distance farther?
     
  6. Jan 31, 2016 #5
    Sorry about the delay I've been really thinking this through. I'm just unsure what is being said by difference of times.
     
  7. Jan 31, 2016 #6

    ehild

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    The first of your problem is how do you get the time you need to cover a distance d with speed v. You travel with speed 100 km/h, what time is needed to reach a town at 200 km distance?
     
  8. Jan 31, 2016 #7
    2 hours
     
  9. Jan 31, 2016 #8

    ehild

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    What is the general formula used to get time from distance and speed?
     
  10. Jan 31, 2016 #9
    d=vt
    t = d/v
     
  11. Jan 31, 2016 #10

    ehild

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    It is correct now. In what time does the echo of the clap return from a wall at distance d? And what is the time of return from a wall at distance d+w?
     
  12. Jan 31, 2016 #11
    The time taken to return back(when the distance is d)
    is equal to 2d/v where v is the velocity of sound
    and when the distance is d+w
    The time taken is 2(d+w)/v
    Therefore
    The difference in the times taken equals 2w/v
     
  13. Jan 31, 2016 #12
    Alright after looking at Uchiha's work that is correct. difference in time represents the period.

    So,

    f = 1/T = v/2w = 343 m/s/2(0.75m) = 230 Hz

    for b) since f is proportional to 1 /w the frequency will be higher
     
  14. Jan 31, 2016 #13
    Precisely,OmniNewton
    Just some thinking and calculations always suffice :)
     
  15. Jan 31, 2016 #14
    Thank You So Much!
     
  16. Jan 31, 2016 #15
    You're welcome!
     
  17. Jan 31, 2016 #16
    Heh thanks mate for those likes!:)
     
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