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: A few sound problems

  1. Mar 15, 2007 #1
    1. The problem statement, all variables and given/known data
    1. An unfingered guitar string is 0.70 m long and is tuned to play E above middle C (330 Hz). How far from the end of this string must the finger be placed to play A above middle C (440 Hz)?

    2. An organ is in tune at 20 degrees C. By what fraction will the frequency be off at 0 degrees C?

    2. Relevant equations

    3. The attempt at a solution

    1. I used the v=(freq)(wavelength) equation:
    v = (330)(0.70) = 231 m/s
    Then i plugged in 231 to figure out the distance for 440 Hz:
    (231 m/s) = (440)x
    x=.525 m
    I'm not sure if my method is right, so please check that! thanks

    2. Not sure about this one

    Thanks for the help
  2. jcsd
  3. Mar 15, 2007 #2
    I think that's right.

    For the second part,
    [tex]v=\sqrt{\frac{\gamma RT}{M}}[/tex] The temperature should be in Kelvin. Since there is no change in the gas, [tex]\frac{\gamma R}{M}[/tex] are constant, and so the speed of sound varies with the square root of temperature. That should help you out.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook