Missing text in the problem (found on internet):
"A 70 cm -long steel string with a linear density of 1.0 g/m is under 200 N tension. It is plucked and vibrates at its fundamental frequency"
Solution:
The frequency of the sound wave along the string is given by
[tex]f= \frac{1}{2L} \sqrt{ \frac{T}{\mu} } [/tex]
where L=70 cm=0.7 m is the length of the string, T=200 N its tension and [tex]\mu = 1g/m =0.001 kg/m[/tex] is the linear density. Using these values in the formula, we find
[tex]f=319.4 Hz[/tex]
