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Homework Help: Phase angle for wave eqn

  1. Sep 25, 2011 #1
    1. The problem statement, all variables and given/known data

    At time t = 0 and at position x = 0 m along a string, a rightward (+x dir) travelling sinusoidal wave with frequency of 230 Hz has displacement y = +4.8 mm and transverse velocity vy = -0.75 m/s.

    What is the smallest positive phase angle?

    What is the amplitude of the wave?

    How long does an observer at x=0 need to wait before a trough (y=-A) arrives?





    3. The attempt at a solution

    .0048=Asin(phi)
    -.75=acos(phi)

    arctan[2(pi)(230)(.0048/-.75)]=phi=-1.463

    pi-1.463=1.678rad

    For some reason this answer is incorrect and I dont know why since I used in my calculation of part B which is correct.

    B) .0048/sin(1.678)=.00483m

    Not sure how to approach part c...

    As always thanks for the help
     
  2. jcsd
  3. Sep 25, 2011 #2
    for c I would just solve t for -A correct, omega would be negative since the wave is moving rightward?

    arcsin(-1)/(-2pi*230)=t=.0011

    Does this make sense?
     
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