# Waves and Pressure Changes

1. Dec 4, 2005

### Seiya

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. Dec 4, 2005

### Staff: Mentor

The general form for a wave is

y(t) = cos ($\omega$t + $\theta$) where $\omega$ is the angular frequency (= 2$\pi$f) and $\theta$ 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$\lambda$, where $\lambda$ is the wavelength.

Another way to write this expression is

y(x,t) = A sin ($\omega$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.

3. Dec 4, 2005

### Seiya

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