A student performs an experiment in which two blocks, block x of mass 2kg and block y of mass 3kg, are tied together by a rope. The system containing block x and block y is dropped above earth’s surface in the orientation shown in figure 1. A motion detector below each block collected data that were graphed to show the velocity as a function of time for blocks x and y as they fell toward the ground. The graphs are shown in figure 2 and figure 3, respectively. The positive direction is considered to be down. The change in momentum for the system containing block x and block y is most nearly