/kloc-After the mid-9th century, natural scientists still haven't completely got rid of the confusion of this debate about motion measurement. According to the latest achievements of natural science, especially the discovery of the law of conservation and transformation of energy, Engels put forward the essential difference between them. Engels pointed out that under the condition that mechanical motion and other forms of motion (such as motion transfer under the condition of simple mechanical balance, motion transfer under complete elastic collision, etc.) do not disappear, the transfer and change of motion can be measured by momentum mv. ). That is to say, "mv is only a simple motion, so it is a measure of continuous mechanical motion", but when mechanical motion "disappears" and other forms of motion are generated, that is, the process of mutual transformation between mechanical energy and other forms of energy (including potential energy, thermal energy, electromagnetic energy and chemical energy), in all these cases, it should be measured as mv2/2. Here, mv2 is a measure of the mechanical motion that has disappeared. In this way, Engels came to the conclusion that there are indeed two measures of mechanical motion, and each measure is applicable to a series of phenomena within a very clear range. In a word, mv is a mechanical movement measured by mechanical movement, and mv2/2 is a mechanical movement measured by its ability to transform into other forms of quantitative movement. In fact, momentum and kinetic energy are not contradictory, because they have different properties and different application ranges. As for the further solution of the two measurement problems, it was after Einstein founded the special theory of relativity.