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Homework Help: Waves and Pressure Changes

  1. Dec 4, 2005 #1
    Say if i have an equation:

    x = cos pi/2 (x-330t)

    someone told me that 330/4 is the period. I just want to know how come.... whats the 330 represent exactly? i tought it was w (angular frequency) which would mean w/2(pi) = f .... and 1/f = T but i dont get the same results as what he said (330/4) = T....

    I'm very confused about this and ive got a test tomorrow... if someone could explain it to me Id very much appreciate it. Thank you
  2. jcsd
  3. Dec 4, 2005 #2


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    The general form for a wave is

    y(t) = cos ([itex]\omega[/itex]t + [itex]\theta[/itex]) where [itex]\omega[/itex] is the angular frequency (= 2[itex]\pi[/itex]f) and [itex]\theta[/itex] is the phase angle, which is based on the initial condition. The period T = 1/f, and if the wave speed = c, then c = f[itex]\lambda[/itex], where [itex]\lambda[/itex] is the wavelength.

    Another way to write this expression is

    y(x,t) = A sin ([itex]\omega[/itex]t - kx), where k is the wave number, and kx is the phase lag. If kx was preceded by +, the it would represent a phase lead.
  4. Dec 4, 2005 #3
    Oh god how embarassing, all this time i was confused about this topic because of a simple MATH error..... i canceled out something i should not have canceled out!!

    Oh my god *blushes* :(

    Thanks for the help... i still can't believe this lol... =\
    Last edited: Dec 4, 2005
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