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!

Doppler Effect

  1. May 22, 2010 #1
    1. The problem statement, all variables and given/known data

    (a) A siren emits a frequency of 900 Hz. Wind is blowing at a steady speed of 15.0 ms-1. The speed of sound in calm air is 343 ms-1. What is the frequency heard by someone approaching at 15.0 ms¹,

    (i) when the wind blows from the person to the siren,
    (ii) when the wind blows from the siren to the person?

    2. Relevant equations

    f'=(1+v_o/v)

    3. The attempt at a solution

    i figured out the relative velocity of the sound (for i 343-15) and then subbed into the formula which became 1+15/328=1.04573HZ. I'm pretty sure this isnt right because the frequency should get higher but mine inst even close.... also i didnt use the given frequency at all????????
     
  2. jcsd
  3. May 23, 2010 #2

    rl.bhat

    User Avatar
    Homework Helper

    Check the formula.
     
  4. May 23, 2010 #3
    That formula is the one in my text book for the observer moving and the source stationary
     
  5. May 23, 2010 #4
    hey, i really need some help with this if you know a different equation i should use?
     
  6. May 23, 2010 #5

    rl.bhat

    User Avatar
    Homework Helper

    The correct formula is

    [tex]f' = [1 + \frac{v_o}{v}]f[/tex]

    Velocity of sound will be depending on the direction of the wind.
     
  7. May 23, 2010 #6
    ok thanks i dont know how i missed the second f...thanks
     
  8. May 27, 2010 #7
    I get (i) 941Hz and (ii) 938Hz

    Does this sound right?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Doppler Effect
  1. Doppler effect (Replies: 3)

  2. The Doppler Effect (Replies: 3)

Loading...