The two balls move from left to right on two parallel straight lines, and the same negative is exposed many times with the current high-speed camera.

From the picture, we can see that the distance between the blue ball and the white ball is getting bigger and bigger, but the distance between the white balls is the same, so the blue ball is accelerating and the white ball is moving at a constant speed.

At T 1, the white ball is behind the blue ball, and at T2, the white ball exceeds the front, so it is an encounter.

The correct view of continuing to look down is to look at only one group at a time and ignore the rest. The blue ball is behind the white ball, which proves that the blue ball has not caught up with the white ball at this time.

At t6, the blue ball overtook the white ball, which was the second encounter, because the blue ball was accelerating. From the same time interval, it can be clearly seen that the speed of the blue ball has surpassed that of the white ball at this time, so it is impossible for the white ball to recover the blue ball in the future and will not meet again.

Don't look at so many points in this picture at the same time, but look at it in groups, each group represents the position of two balls at a time point, so it is easy to understand.

It is also clear in the title that when two balls have the action of surpassing each other, they are regarded as meeting. In the whole process, the white ball overtook the blue ball once in front, and then the blue ball overtook the white ball because the blue ball accelerated and the white ball was uniform. After that, the white ball is even, so it is impossible to catch up with the blue ball. * * * is the process of surpassing each other twice, so I met twice.