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!

Wave Equation

  1. Mar 16, 2007 #1
    1. The problem statement, all variables and given/known data

    The displacement of particles in a string stretched in the x direction is represented by y. Which of the following expressions for y describe wave motion:

    1: cos kx sin wt

    2. Relevant equations

    Equation of a progressive wave is of the form [tex]y=f(t-\frac{x}{v})[/tex]

    3. The attempt at a solution

    The first equation represents a standing wave. The second obviously cant be it (its not of the form f(t-x/v) ). But I thought the third one would represent the equation of a progressive wave. It doesnt though. Why?
  2. jcsd
  3. Mar 16, 2007 #2
    wt+kx=w(t-k/w x')=w(t-x'/v)
    (using v=w/k)
  4. Mar 16, 2007 #3
    Yeah. I got that. But it isnt the answer. The third equation doesnt represent a wave. Why?
  5. Mar 16, 2007 #4
    Why not?

    cos^2 (wt-kx')=1/2+1/2cos(2[wt-kx'])

    so the fn=A+Bcos(w't-k'x')

    Looks like a sinusoidal wave to me.

    What's wrong with using a standing wave? Isn't that what you'd get in a stretched string?
  6. Mar 16, 2007 #5
    Yeah, you get a standing wave cause of superpoosition in a string. The thing is, that only one answer is correct. Maybe the language points to a standing wave?
  7. Mar 16, 2007 #6
    You get a standing wave, because the string is stretched- so it must be held at both ends.
  8. Mar 16, 2007 #7
    If a string is stretched, it doesnt necessairily mean that you would have to get a standing wave.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Wave Equation
  1. Wave equation (Replies: 2)

  2. Wave equation (Replies: 4)

  3. Wave Equation (Replies: 1)

  4. Equation of a Wave (Replies: 4)

  5. Wave equation (Replies: 1)