The mass of a string is 5.40 10-3 kg, and it is stretched so the tension in it is 215 N. A transverse wave traveling on this string has a frequency of 260 Hz and a wavelength of 0.60 m. What is the length of the string

= 7.56 * 10^-9 W

Explanation:

1) v  =  √(T/m)

v is the velocity of a wave on the string

T is the Tension

m is the mass of a unit length ( mass of a 1 m length of the string)

   v =  f.λ

√(T/m) = fλ

√(195/m) = 260 * 0.6

we don't know m because we don't know the length

√(195 / m)    = 156  

  195/m        =  156²

  195 / m      =  24,336  

           m      =  195 / 24,336

           m      =   0.008 kg/m

now we know the mass of a unit length

m  =  M / l

M is the mass of the string

l is the length of the string

0.008 =  2.8 * 10^-3  / l

    l     =  2.8 * 10^-3 / 8 * 10-3

   l     =   2.8 / 8

   l     =  0.35 m

OK that's the answer, hope you understood.

2) Power on a unit area is 3.6 * 10^-6  W/m²

so to find the power on a specific area,  just multiply the area by the sound intensity

assuming the ear's flat area is the specified value

power intercepted by ear = (3.6 * 10^-6 W/m²) *( 2.1 * 10^-3 m²)

                                           = 7.56 * 10^-9 W