Final answer:
To determine the y-coordinate when moving backwards to an x-coordinate of 0, additional information or context is typically required. In a physics context, if the movement goes back to the launch point on a flat surface, the y-coordinate would also be 0, indicating no vertical displacement.
Step-by-step explanation:
When moving backwards to an x-coordinate of 0, it's important to establish whether or not additional information is given to determine the corresponding y-coordinate. In many situations, additional context such as a function describing the relationship between x and y, or a graph is needed to accurately provide an answer. However, since the given information implies a context of physics and motion, and mentions "the position y is zero for both the launch point and the impact point", it is reasonable to infer that if by moving backwards to an x-coordinate of 0 implies returning to the initial position, then the y-coordinate would also be 0 in a scenario where the surface is flat and horizontal. This situation represents a displacement of zero, where the initial and final positions are the same, regardless of the path taken.