# Homework Help: Wavefunction of waves

1. May 26, 2010

### Philip Wong

hi guys,
two questions for today one real quick one (the velocity of waves), and one I need help on how to calculate velocity for wave function of waves.

1. The problem statement, all variables and given/known data

1) a ocean weave with a wavelength of 120m are coming in a a rate of 8 per minutes, what is the speed.

2)The wave function of a wave is described by: y=0.02sin(30x-400t), what is the velocity

2. Relevant equations
1) lambda = v/f , therefore v= f*lambda. Given f = 8/60 = 0.133

2) I don't know which equation to use, but I'm thinking about v=-wAsin(wt + sigma) ?

3. The attempt at a solution
1) v= 0.133*120= 15.96 m/s

really confused on how to do 2). can someone give me a step by step walk through on how to derive to a solution!

thanks!

2. May 27, 2010

### nickjer

The analytic form for a wave moving to the right is:

$$y = A\sin(kx-\omega t)$$

So knowing this and the velocity equation you wrote out in Relevant equations (1), you can solve for this wave's velocity.

3. May 28, 2010

### aim1732

Another way is to differentiate the argument of the sine func.(the phase) with respect to time and equate it to zero.