Question

in this y=Acos(kx-wt)

what is k called?is this phase difference or phase constant or phase angle

Answer 1

k is called wave number of wave and it is equal to the number of wavelengths per $2\pi$units of distance travelled by the wave, i.e.
$$\begin{gathered} k=\frac{2\pi }{\lambda } \\ where \\ \lambda =wavelengthofwave \end{gathered}$$