# Waves on water

 P: 5 1. The problem statement, all variables and given/known data A water wave traveling in a straight line on a lake is described by the equation $y(x,t)=(3.75\,\text{cm})\cos(0.450\,\text{cm}^{-1}x+5.40\,\text{s}^{−1}t)$ where $y$ is the displacement perpendicular to the undisturbed surface of the lake. How much time does it take for one complete wave pattern to go past a fisherman in a boat at anchor? What horizontal distance does the wave crest travel in that time? 2. Relevant equations $\omega = 2\pi f$ $k=\frac{2\pi}{\lambda}$ 3. The attempt at a solution This is part of an online test we were asked to submit. For the first part I got $t=1.16\,\text{s}$ which was correct. For the second part I got the wavelength as the answer, $\lambda = \frac{2\pi}{0.0045} \approx 1396\,\text{m}$. However, the online assessment tells me that the correct answer is $0.140\,\text{m}$. Can anyone explain where I went wrong? (This is also question 15.10 in University Physics with Modern Physics International Edition, 13th Edition, if anyone should happen to have the solution manual to such a thing)