Calculating Fundamental Frequency and Overtone Frequency of a Stretched Wire

[i'mcheche]

Homework Statement

a flexible wire is 80 cm long has a mass of 0.40g. It is stretched across stops on a sonometer that are 50 cm apart by a force of 500N. Find the fundamental frequency with which the wire may vibrate. If it vibrates in 2 third overtone, what is it's frequency?

Homework Equations

$$f=\frac{1}{2L}\sqrt{\frac{T}{\frac{m}{L}}}$$

The Attempt at a Solution

I don't kno where to start. I substituted all the given data. And I'm not really sure about my answer.

I can't decide what length should be used in the equation. the problem states the total length of the wire and the length of the wire which is streched on the sonometer.

 

[nil1996]

welcome to PF

it is said that the sonometer stops are 50cm apart.So that should me the length.

 

[jtbell]

There are two L's in the equation. Are they necessarily the same?