A momentum vector diagram shows the momentum of each object in a system at some initial and later time. Typically, you should also include the system’s total momentum and any changes in momentum.
Two objects are moving toward each other. Object 1 has a larger mass and is initially moving to the right. Object 2 has a smaller mass and is initially moving to the left. They collide and end up not moving! Draw and label a momentum vector diagram for this context.