Two identical blocks, A and B, are on a horizontal surface, as shown above. There is negligible friction between the surface and the blocks. As shown in Figure 1, block A is initially moving toward block B with speed vA=v0 and block B is initially at rest. Figure 2 shows the blocks in contact as they collide a short time later. In both figures, the location of the center of mass of the two-block system is indicated by the X that is labeled CM.

During the time that the blocks are in contact, describe whether the center of mass of the two-block system is speeding up, slowing down, or staying the same. Speeding up Slowing down Staying the same Briefly describe, in terms of a basic law of physics, whether the center of mass of the two-block system is speeding up,