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Homework Help: Speed of Sound Calculations. Confused.

  1. Sep 12, 2010 #1
    1. The problem statement, all variables and given/known data

    We have to prove the speed of sound using a ultra-sound emitter, connected to EasySense software which records the speed for it to travel to surface and back. Known data - Speed of sound is 337 metres a second at 20 degrees celcius. Also, the distance covered is, 3.4m or 6.8m there and back. The time is 0.010837 micro seconds. Micro-seconds are 1 x 10^-6. All answers must be given with a +- .

    2. Relevant equations

    Speed = Distance / Time

    3. The attempt at a solution

    Time: 10897 +- 14 (microsecs)
    Dist: 6.8 +- 0.014 (metres)

    Convert microseconds into seconds. 10897 / 1000 and then /1000 again.
    = 0.010897 seconds

    Speed = 6.8 / 0.010897 = 624.024961 metres per second.

    Obviously, this is nearly double the actual speed of sound. Was I not meant to double the distance? But I'm pretty sure the time is for there and back so double distance was needed. Have I forgotten anything? Of course, there is a chance the Ultrasound was reflecting from a place not wanted, causing the distance to not be true.

    Help much appreciated.
  2. jcsd
  3. Sep 13, 2010 #2
    You have very different times in 1 and 3 above. Could you also have misunderstood the distance?
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