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: Finding phase difference based on distance

  1. Feb 22, 2010 #1
    1. The problem statement, all variables and given/known data
    A tuning fork is in a hall 47.0 m long, and is placed 14.0 m from one end. It generates a tone of 246Hz. What is the phase difference when the waves traveling in each direction bounce back and meet each other?


    2. Relevant equations
    Calculated wavelength with 343/246. Also tried 2pi*38m/1.39m = phi. Also maybe (cos phi/2)sin(kx-omega*t+phi/2)



    3. The attempt at a solution

    Well, I figured that I could make it simple, calculate the wavelength, divide the difference in distance traveled by wavelengths, getting 27.4 waves, and then multiply .4 * 360 to get things into degrees. This gives me 144 degrees, but the answer in the back of the book is 91.3 degrees. What am I doing wrong?

    Thanks in advance.
     
  2. jcsd
  3. Feb 23, 2010 #2
    Had a chance to talk to the prof, and it turns out my method was correct, but my sig figs were off. Apparently, to get a correct answer, it was necessary to assume the distances were correct to about 5 sig figs, even though the book conventionally requires only 3 and the givens were all in 3 sig figs. Poorly written question IMO.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook