Catch-up and encounter are common problems in kinematics research when two objects move on the same straight line, and they are also concrete applications of uniform and variable speed motion laws in practical problems. 1. The main condition of chasing is that two objects reach the same position at the same time in the process of chasing. In the process of catching up, when the speed of the pursuer is greater than that of the pursued, the distance between them decreases; When the speed of the pursuer is less than that of the pursued, the distance between them increases. There are three common situations: (1) When a uniformly accelerating moving object A with zero speed chases a uniformly moving object B in the same direction, it will definitely catch up. Before catching up, the condition of the maximum distance between two objects is that the speed of the two objects is equal, that is, V A = V B. (2) When the object A moving at a uniform speed catches up with the object B moving at a uniform speed in the same direction, there is a critical condition of just catching up and just not catching up: the speed of the two objects is equal. The specific method is: assuming that both can reach the same position, compare their speeds at this time, if V A >；; V B, you can catch up, if V a