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!

Standing wave equation set up

  1. Sep 30, 2015 #1
    1. The problem statement, all variables and given/known data
    upload_2015-9-30_6-19-51.png

    2. Relevant equations

    y (x,y) = 2YmSin(kx)Cos(wt)


    3. The attempt at a solution

    I am having trouble at setting up the standing wave equation for this problem.

    Once I set up the equation, I know that part a b c d is just plugging in the numbers.

    From what I learned, I know that the standing wave equation is

    Y(x,y) = 2YmSin(kx)Cos(wt), this is what the textbook states.

    (Ym being the amplitude).

    I calculated k and w correctly.

    The equation I set up was Y(x,y) = .041Sin(kx)Cos(wt)

    However, the solution uses the equation

    Y(x,y) = -2YmCos(kx)Sin(wt).

    therefore,

    Y(x,y) = -.041Cos(kx)Sin(wt)

    I do not understand why there is a negative sign in front of the amplitude and why Sin and Cos is switched in the equation used by the solution.

    Any help or guide will be greatly appreciated, Thank you.
     

    Attached Files:

  2. jcsd
  3. Sep 30, 2015 #2

    RUber

    User Avatar
    Homework Helper

    The form used in the solution is based off the plot. The plot at x = 0, with t varying implies that the kx term has to be inside a cosine function--otherwise your plot at x = 0 would be a flat line. The plot shows at t=0, y=0, so the wt term should be inside a sine function. Finally, the y value first dives into negative territory, as t is small and positive, so you would want a negative sine of wt function in order to do that.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Standing wave equation set up
Loading...