Answer
$v = 28.6~m/s$
Work Step by Step
We can find the tension $\tau$ in string 1 and string 2:
$2\tau = Mg$
$\tau = \frac{Mg}{2}$
$\tau = \frac{(0.500~kg)(9.8~m/s^2)}{2}$
$\tau = 2.45~N$
We can find the wave speed on string 1:
$v = \sqrt{\frac{\tau}{\mu}}$
$v = \sqrt{\frac{2.45~N}{0.00300~kg/m}}$
$v = 28.6~m/s$
