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Test On Monday please help

  1. Dec 2, 2007 #1
    Test On Monday...please help!!!

    1. The problem statement, all variables and given/known data
    My home is exactly 7.8 km from the Stadium where the 4th of July fireworks are held. The time difference between when I see a flash and when I hear the corresponding sound is 22.4073542085608 s. What is the temperature (in degrees Celsius) of the air?

    2. Relevant equations
    Vsound = sqrt (GAMMA * R * T) / M

    3. The attempt at a solution
    T = 20 degrees Celsius + 273 = 293
    V = 7800/22.4073542085608 = 348.1 m/s

    T = Vsound^2 * M / GAMMA * R

    But I don't know M, GAMMA, or R???
  2. jcsd
  3. Dec 2, 2007 #2


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    Staff: Mentor

  4. Dec 2, 2007 #3

    Doc Al

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    Staff: Mentor

    With 16 significant figures, whoever devised this problem has a sense of humor. :rolleyes:


    R is a universal constant; gamma and M are constants specific to air. Read all about it here: Sound Speed in Gases

    Astronuc beat me to it!
  5. Dec 2, 2007 #4
    lol I know I love the 16 sig figs. So I understand that...but she showed us this way...
    T = ((vsound - 331 m/s) / 0.6 m/s) °C
    = ((348.1 m/s - 331 m/s) / 0.6 m/s) °C
    = 28.5 °C

    And I am don't know where she got that equation and some of the numbers from?
  6. Dec 2, 2007 #5

    Doc Al

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    Staff: Mentor

    The link I provided derives that exact equation.
  7. Dec 2, 2007 #6
    oh yea I am sorry I didn't scroll down.
  8. Dec 2, 2007 #7
    can someone please help me?
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