# Vibrations in Waves

1. Feb 20, 2008

### petern

1. The problem statement, all variables and given/known data
A guitar string is set in vibrations at a frequency of 437 Hz. How many vibrations did the guitar's string make while the sound propagated 235 m in the air?

2. Relevant equations

V = wavelegth x freq.

3. The attempt at a solution

I figured out that you do 437 Hz x 235 m = 102695 m/s. 102695 / 343 = 299.4 vibrations.

Can anyone explain how this works? I thought vibration was the frequency. I don't understand how the vibration represents how many times faster than the speed of sound it is.

2. Feb 20, 2008

### Jakell

first you want to figure out how long it takes the sound to travel the 235 meters. if you know that, you can use the frequency to figure out how many times the string vibrates in that period.

3. Feb 20, 2008

### Tedjn

The vibration is the frequency. What you did gave you the right answer, but it was done in the wrong order. Following what Jakell said, you would want to first find the time it takes sound to travel 235 meters, which is (235 m)/(343 m/s) [if you are using 343 m/s for speed of sound]. Then you would use the frequency. You end up with the same operations, hence the same answer.

4. Feb 20, 2008

### petern

How would I make a working equation for that? I currently have vibration = (x/v) x f. I used x = xo + vt but I don't know which eq. to use to add the f in.

Last edited: Feb 20, 2008
5. Feb 20, 2008

### Tedjn

What equation do you mean? You have one: # of vibrations = (x/v) * f