1. Not finding help here? Sign up for a free 30min 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!

Sound: freq moving sources

  1. Jun 28, 2003 #1


    User Avatar

    A train is traveling toward you at 120km/h. The train blows its 400Hz whistle. take the speed of sound to be 340m/s. whats the frequency do you hear?

    400/(1-(4.32x10^8 / 340)) i got 4.32x10^8 = 120000m * 3600sec

    what am i doing wrong?
    The possible answers are: which is it and what have i done wrong to miss this test question?

    a) 444hz
    b) 364hz
    c) 361 hz

    Dx :wink:
  2. jcsd
  3. Jun 28, 2003 #2

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    You made a mistake converting the speed of the source from km/h to m/s. If you look at it, you have the source moving faster than light, which is a big no-no.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?