(Continued from Part I).
Sixth, the re-understanding of physical phenomena such as collisions.
When studying problems such as collisions between objects, because such interaction processes between objects have very explosive expressions, people will think that in the process of such interactions, there is a lack of concepts of "action process" and "action time", but in fact this is not the case. Because, the interaction between objects will have a process of action, but the length of the process is different in time.
For example, in the process of pushing a cart, people can make good use of the physical quantity of time to grasp the relationship and connection between various physical quantities between objects. However, when two small balls collide, the action time is so short that it is almost negligible intuitively, and it becomes very difficult to use the concept of time to deal with related problems. In the face of such problems, people have come up with formulas for the relationship between momentum and momentum based on experimental experience, and experience has proved that it will be relatively simple to deal with such physical problems.
Therefore, it can be said that it is very necessary to establish the concept of momentum and calculate the test. After all, when dealing with such problems, the accuracy requirements are not high, and the equations are easy to use, so why not?However, this empirical equation cannot be used as a universal law of physics, because beyond this scope of application, the flaws and failures of the equation will be highlighted.
In fact, even in the interaction between objects, such as collision, it still belongs to the category of mechanical motion of objects, and there are also physical processes such as force, work, acceleration, energy exchange and energy transfer, which are also completely regulated by the laws of motion mechanics.
For example, if a moving ball A collides with a stationary ball B, there is also a process of pushing. In this process, the two balls carry out the exchange and transfer of kinetic energy. Ball A pushes ball B, ball A does work, and kinetic energy decreases;When the B ball is pushed by the A ball, there is a corresponding acceleration, velocity, and increase in kinetic energy. And the amount of kinetic energy reduction of ball A is theoretically equal to the amount of kinetic energy increase of ball B (in the case of low requirements). See, here, the laws of physics of motion mechanics are fully applicable and fully explainable when dealing with such problems.
This is only due to the short interval of action, which people cannot intuitively perceive well, rather than the process and amount of time that does not have an effect. The amount of this time period can be millisecond-level, if not, then microseconds, femtoseconds, after all, there is. In this short interval of time, the process of force, work, acceleration, distance, and transfer of kinetic energy between the two small balls is completed. This is fully in line with the law of conservation of energy, and the causal relationship between various physical quantities can be fully established. In addition, according to the known conditions, it is possible to calculate the values of each physical quantity.
In this collision process, the kinetic energy lost by ball A is equal to the kinetic energy increased by ball B, and because ball A and ball B share the kinetic energy of the original ball, the calculated velocity is also relatively accurate. It is precisely because of the interaction between the spheres A and B that the gains and losses of energy are consistent and equal in quantity (in the case of ignoring energy consumption). This also explains why objects with less mass move faster after a collisionThe reason for the slow movement of objects with large masses. Since, in the expression of kinetic energy, is the product of the mass of the object and the square of the velocity. And the mass is constant, the gain and loss of kinetic energy is comparable, and of course there will be the physical fact that the smaller the mass, the faster the speed.
When we can clearly understand these related physical contents, we should know that the so-called "law of conservation of momentum" does not exist, and only the "law of conservation of energy" is the fundamental law of motion mechanics.