Physics

Problem

At a fixed position

x=0

, the vertical displacement of a point on a string is given by

y(0,t)=0.040\,\text{m}\,\cos(100\pi t)

. The wave propagates along the string toward increasing

x

with speed

20\,\text{m\,s}^{-1}

. Determine the wave number

k

of this sinusoidal wave.