Problem 13.22

13.22. a)
We first note that
$\mu = 30 g/m$
We can also find the wavelength by noting that there are 4 complete waves in a 6 m segment.
$\lambda = 1.5 m$
We also note that
f = 50 Hz
$\omega = 2\pi f ~=~ 314 s^{-1}$
A = .075 m
Now, we can write an equation for the wave travelling on the string.
$y(x,t) = A \sin (\frac{2\pi}{\lambda}x - \omega t)$
$y(x,t) = (0.075 m) \sin (4.19x - 314t)$

b)
We know that power is given by
$P = \frac{1}{2} \mu \omega^{2} A^{2} v$
P = 625 W