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: Doppler Effect question

  1. Nov 6, 2013 #1
    1. The problem statement, all variables and given/known data
    Two trains are traveling toward each other at 30.0 m/s relative to the ground. One train is blowing a whistle at 480 Hz. (a)What frequency is heard on the other train if the wind is blowing at 30.0 m/s toward the whistle and away from the listener? (assume the speed of sound is 343m/s)

    2. Relevant equations

    3. The attempt at a solution
    Well the top velocity has a + and the bottom has a minus because they're going towards each other and the wind is going away from the listener and towards the source.
    So I just assumed F'=480((343+30+30)/(343-30+30)) since this is the vector sum? This is wrong however and it's actually the opposite, so I need help understanding why conceptually
  2. jcsd
  3. Nov 6, 2013 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    You need to take each speed relative to the medium.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted