1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Find the speed of sound

  1. Apr 15, 2017 #1
    1. The problem statement, all variables and given/known data
    In this part of the lab you tracked a single peak as you moved a microphone in order to get a good value of the speed of sound. This question will lead you through a similar process with just two measurements.

    (The lab set up: speaker emitting the signal faced one microphone a certain distance x away. Measure Δt of the same peak in both positions)

    The graphs below show two sine-wave signals like you saw from a microphone positioned in front of a speaker in Part 3 of the experiment. The two dashed vertical lines represent the cursors of the oscilloscope, with the one on the right side (colored orange) tracking a peak of the sound wave as the microphone is moved. The position x of the microphone in front of the speaker and the time between the cursors Δt is shown below each graph.

    Mic position: x = 5.00 cm. Cursor difference: Δt = 0.0828 ms
    Mic position: x = 20.0 cm. Cursor difference: Δt = 0.511 ms
    Answers have to be correct within 2%

    2. Relevant equations

    velocity = Δx / Δt

    3. The attempt at a solution
    convert all units to standard units
    1) mic position = .05 m , cursor difference = 8.28 * 10^-5 s
    2) mic position = .2 m , cursor difference = 5.11*10^-4 s

    velocity = (.2 - .05) / (4.282 * 10^ -4)
    velocity = 350.3 m/s

    I input this answer online, but it says it is wrong... check rounding or significant figures. I tried slightly different numbers, like rounding 4.282 * 10^-4 to 4.28 * 10^-4, giving me an answer of 350.5 but it is still wrong... rounding it up to 351 doesn't work either and I suspect rounding down to 350 also will not work because it is within 2% of my initial answer.... did I make some kind of mistake elsewhere?
  2. jcsd
  3. Apr 16, 2017 #2


    User Avatar
    2017 Award

    Staff: Mentor

    I get the same result.

    There is no obvious modification that would lead to an answer more than 1% away but still within realistic values for the speed of sound.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted