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Homework Help: Tank position problem based upon sound of fire

  1. Dec 12, 2008 #1
    1. The problem statement, all variables and given/known data

    An approaching tank fires at you and you hear the sound 3 seconds after the muzzle flash. Ten seconds later the same tank fires again and you hear the sound 2 seconds after the flash. The temperature is 100 degrees Celsius. How fast is the tank going? How long until he reaches you.

    2. Relevant equations

    v=331.4 + .606Tc that is the speed of sound in air based upon the temperature.
    v= wavelength symbol X frequency
    These are the only ones i think that could help me but i could be mistaken.

    3. The attempt at a solution

    So i know the speed of sound in air is 392 meters/sec based upon the equation v=331.4 + .606Tc

    v= 331.4 + .606(100)
    v= 331.4 + 60.6
    v= 392 m/s

    I can't figure out where to go from here. to get the other answers thank you for any help
  2. jcsd
  3. Dec 12, 2008 #2


    User Avatar
    Homework Helper

    Welcome to PF.

    First of all you might want to check the ambient temperature of the terrain, because 100° C is a prodigious life stopping temperature. 100° F maybe?

    In any event ...

    At the first shot the speed of the bullet lagged the firing by 3 seconds. In 10 seconds later it lagged by 2.

    So ...

    In 10 seconds the tank covered the distance that sound covered in 3 - 2 = 1 seconds. The rank is traveling then at 1/10 the speed of sound.

    Resolve the temperature and you should be on the sunny side of the street.
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