# Third harmonic frequency

1. Sep 24, 2015

### goonking

1. The problem statement, all variables and given/known data
A metal wire is vibrating at its third-harmonic frequency. 0.32 m from one end, the amplitude is equal to one quarter the maximum amplitude. Find the length of the wire.

2. Relevant equations

3. The attempt at a solution
I don't quite understand the question, it says 0.32m from one end, is that from the start to the first node?

the amplitude going to be 1/4 its maximum where sin(x) = 0.25, correct?

2. Sep 24, 2015

### haruspex

It is not clear to me whether the wire is fixed at either or both ends. I'd guess it's fixed at both. If so, the 'start' is a node, and .32m is the distance from there to the given point.
It depends what you mean by x.

3. Sep 24, 2015

### goonking

if it helps, the hint the question has is : "The third harmonic will have a wavelength equal to 2/3 of the length of the string. Also, *note to self* the max-amplitude of this wave is (2A) not (A)."

4. Sep 24, 2015

### haruspex

So what does that tell you about whether one or both ends of the string are nodes?