Time difference between two sine waves

  1. "There are two sine waves having a phase difference of 20 degrees. After one reaches its maximum value, how much time will pass until the other reaches its maximum, assuming a frequency of 60 Hz."

    Should I go about this by assuming...
    sin(120pi*t) = sin(120pi(t + x) - 20)

    Any hints appreciated
  2. jcsd
  3. Galileo

    Galileo 1,999
    Science Advisor
    Homework Helper

    You have two sines which have are functions of position and time. (actually, considering them function of time alone is sufficient)
    They both have the form:
    [tex]A\sin(kx-\omega t + \phi)[/tex]

    Assume the first wave reaches its maximum A at time t=0 and position x=0.
    Then you have to find t when the second wave reaches its max A:

    [tex]A\sin(-\omega t + \phi)=A[/tex]
    Where [itex]\phi[/itex] is 20 degrees expressed in radians.
    Last edited: Nov 20, 2004
  4. I get it. Since 20 degrees = pi/9, moving LHS A to RHS gives
    sin (-120pi*t + pi/9) = 1
    so, -120pi*t + pi/9 = pi/2
    and finally t = 7/2160 seconds

    Many thanks
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