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Homework Help: What frequency does the blood receive? What frequency return

  1. Dec 9, 2015 #1
    1. The problem statement, all variables and given/known data
    Ultrasound reflected from an oncoming bloodstream that is moving at 28.7 cm/s is mixed with the original frequency of 2.41 MHz to produce beats. Use the speed of sound in human tissue as 1540 m/s. Assume that the frequency of 2.41 MHz is accurate to seven significant figures. (Hint: compare to Example 17.8 in OpenStaxCollege Physics.)

    a) What frequency does the blood receive? (Give an answer in MHz, to 7 significant figures.)

    b) What frequency returns to the source? (Give an answer in MHz, to 7 significant figures.)

    c) What beat frequency is produced if the source and returning frequencies are mixed? (Give an answer in Hz, to 3 significant figures.)

    2. Relevant equations

    f(observed) = f(s) x (Vw / Vw +/- Vs)

    f(observed) = f(s) x (Vw +/- V(obs)) / Vw

    3. The attempt at a solution

    (2,410,000 Hz)(1540 m/s + .287 m/s) / 1540 m/s) = 2410449.136 Hz = 2.410449 MHz

    (2410449 Hz)(1540 / 1540 - .287) = 2410948.313 Hz = 2.410948 MHz

    c) 2410948.313 - 2410000 = 948 Hz

    a) is correct, I got that one right. b) and c) are wrong. I thought I did them correctly. Could someone please help?
    Thank you!
  2. jcsd
  3. Dec 9, 2015 #2
    NEVERMIND! I solved it
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