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Homework Help: Phase angle of a string

  1. Apr 5, 2008 #1
    A transverse, sinusoidal wave is traveling along a string. It moves in the negative x-direction, and it has an amplitude of 5 cm. At time t=0, the point at x=0 is at a displacement of 4 cm and is traveling upward. What is the phase angle in degrees?

    2. Relevant equations
    x = A*cos([tex]\omega[/tex]*t+[tex]\phi[/tex])

    3. The attempt at a solution

    At t=0, [tex]\omega[/tex]*t = 0, so x = A*cos([tex]\phi[/tex]). Therefore, [tex]\phi[/tex] = arccos(x/A) = arccos(.8) = 36.87.

    The acceleration is negative and the velocity is positive, so the angle is 360 - 36.87 = 323.13 degrees, right?
  2. jcsd
  3. Apr 6, 2008 #2
    The equation you just used is not trustworthy for waves.It can be only generalized to SHM.

    You must use wave equations to be more sure in your answers.

    y= A sin ( k*x-omega*t + phase angle)
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