# Wave Equation problem Help

1. Jan 25, 2006

### Ishu

Wave Equation problem..!!! Help...!!!

Hi can anyone solve this??
I couldnt figure out how to use it

Question
Use the wave equation to find the speed of wave given by

y(x,t)=(3.00 mm) sin [(4.00/m)x-(7.0/s)t) ]

I guess the wave equation is ,

(d^2y) 1 (d^2y)
------- = ------ -------
(dx^2) v^2 (dt^2)

can any one solve it step wise?

2. Jan 25, 2006

### Päällikkö

Not really, no. That's not quite how stuff's done on this forum. You're supposed to do the work yourself.

The wave equation:
$$\frac{\partial ^2 y}{\partial x^2} = \frac{1}{v^2}\frac{\partial ^2 y}{\partial t^2}$$

For the given wave, can you solve
$$\frac{\partial ^2 y}{\partial x^2}$$ and $$\frac{\partial ^2 y}{\partial t^2}$$ ?

3. Jan 25, 2006

### Ishu

I mean need some hint......

please I ahve 1 more hrs left

4. Jan 25, 2006

### Ishu

Am i suppose to t6ake second derivative of whole equation...twice? once with respect to t and again with respect to x?
is that how I am supposed to do?

5. Jan 25, 2006

### Päällikkö

Yep, that's what you're supposed to do.

6. Jan 25, 2006

### Ishu

that means I am supposed to solve for "V" right?

But the answer I got is not the same as the one I got from V=w/k

??

7. Jan 25, 2006

### Päällikkö

It should be the same, as the equation reduces to $$v = \frac{\omega}{k}$$