The diagram depicts a stationary wave, at time $t = 0$, that has been produced on a string held fixed between points P and S. The nodes of the stationary wave are located on the string at P, Q, R and S. At time $t = 0$, point X is moving downward. The points on the string oscillate with time period $T$ and a maximum amplitude of $2\ \text{cm}$. The displacement $s$ is taken to be positive upwards. Which graph most accurately shows how the displacement $s$ of point Y on the string changes with $t$?
Physics 9702 · AS & A Level · Stationary waves