Question

Why is the direction of position V upwards?

Answer 1

Answer:

The wave is moving from left to right (as indicated by the arrow), so, given that at the current instance the amplitude of the position V is 0 (or whatever midpoint the dashed line corresponds to), in the immediately next instance the position will continue increasing as the wave moves from left to right. The peak currently shown at U will at some point "arrive" at V. At that point the location V will have the maximum amplitude. After that the direction at position will be downward, etc.