1. The problem statement, all variables and given/known data http://i1269.photobucket.com/albums/jj597/bubakazouba/114d22d10848ac93ac2fcea482ffe527_zpsedb41f24.jpg [Broken] the other line is a drawing of me trying to trace the wave(but of course its wrong,Im sry try to ignore it) the answer is A 2. Relevant equations My teacher told me that when we get a question like this to determine the point that I want to track its path and look at its left to see whether the point on its left is higher or lower than it if it is lower then it will go downwards and vice versa. 3. The attempt at a solution I tried that but it gets Q wrong, Q should get downward, why is it stationary? which leads to the other question how can any point on the wave remain stationary after a time.