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!

Simple wave problem - phase constant

  1. May 5, 2016 #1
    1. The problem statement, all variables and given/known data
    The figure shows the displacement y versus time t of the point on a string at x = 0, as a wave passes through that point. The scale of the x axis is set by ys = 84.0 mm.The wave has form y(x, t) = ym sin (kx - ωt+φ). What is φ? (Caution: A calculator does not always give the proper inverse trig function, so check your answer by substituting it and an assumed value of ω into y(x, t) and then plotting the function.)

    2. Relevant equations
    y(x, t) = ym sin (kx - ωt+φ)

    3. The attempt at a solution
    This is supposed to be really easy but the solution I got was wrong. My approach was straight forward:
    read off the initial y value --- y(0,0)=0.028
    and sub in the equation: 0.028=0.084sin(0-0+φ)
    φ=arcsin(0.028/0.084)=0.339836.......=0.340 rad
    The question mentioned that the calculator might give the wrong value but I do not see how I could make amend to it.
    Please enlighten me!
     

    Attached Files:

  2. jcsd
  3. May 5, 2016 #2

    blue_leaf77

    User Avatar
    Science Advisor
    Homework Helper

    At ##x=0##, you have ##y = -A\sin(\omega t -\phi)##, this is the curve ##y = -A\sin(\omega t)## translated by ##\phi##. When you compare ##y = -A\sin(\omega t)## with the picture you uploaded, you should see that ##\phi## should be in the second quadrant.
     
  4. May 5, 2016 #3
    I see where I went wrong, thank you very much for the help!
     
  5. May 5, 2016 #4
    Though, are you sure its in the second quadrant? I think it should be π+0.340 and thats third quadrant
     
  6. May 5, 2016 #5

    blue_leaf77

    User Avatar
    Science Advisor
    Homework Helper

    That cannot be the case because sine of an angle in 3rd quadrant is negative, on the other hand the displacement is positive in your picture.
     
  7. May 5, 2016 #6
    So it would be π-0.34? This gives a value thats in the 2nd quad
     
  8. May 5, 2016 #7

    blue_leaf77

    User Avatar
    Science Advisor
    Homework Helper

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: Simple wave problem - phase constant
  1. Simple wave problem (Replies: 2)

Loading...