In the wave equation y = 0 . 5sin(2π)/(λ)(400t - x)m the velocity...

Given equation of the wave is $y = 0 . 5\sin \left(\dfrac{2\pi}{\lambda}400t - \dfrac{2\pi}{\lambda}x\right)$

Comparing it with the standard equation of motion $y = Asin\left(\omegat - kx\right)$ we get,

$\omega = \dfrac{2\pi}{\lambda}400$ and $k = \dfrac{2\pi}{\lambda}$

Now the velocity of the wave will be,

$v = \dfrac{\omega}{k} ⇒ v = 400m{s}^{- 1}$