Several problems of momentum impulse of vector torque rotating power

Let me talk about my personal opinion. These don't necessarily come from where I saw them. Some of them are just my own ideas. Don't believe it all:

1. Whether a physical quantity is a vector, that is, whether it has a direction, is generally decided in books. For example, force is a vector and temperature is a scalar. But I think whether vectors exist depends on your need to solve problems, and vectors are just a way for people to solve problems. For example, force is a vector: but if it is only used to study the force on the rope, it can be solved by saying that it is a scalar. Another example is that the temperature is a scalar. If there are two points and three points that affect a result, we may use it as a vector and find a suitable analytical formula. Or when dealing with problems in a one-dimensional coordinate system, it is the same as a vector. Therefore, whether the vector is artificially defined is just that everyone agrees that it is reasonable to use it, so let's use it.

2. Torque is a vector, and so is the torque to the axis, but the torque to the axis is a concrete model, not the torque to the axis. Generally speaking, the force is perpendicular to the axis direction, and only rotation around the axis is considered. At this time, it is only clockwise and counterclockwise, so it can be solved as a scalar. In fact, it has a direction (of course, it is conventional), that is, along the axis. I don't think I need to say anything more.

In addition (4), in an ideal situation, of course, you can always accelerate, but only in an ideal situation, because when the speed is infinite, the power required is infinite, and such things cannot be found.

Let's put it this way: when the speed of the object and the belt are equal, the object and the belt are in a static friction state, so energy is no longer consumed. The process of consuming energy is the process of accelerating as soon as the object is put on. At this time, there is sliding friction between it and the belt. Of course, the influence of object pressure on friction is not considered. At this time, it should be calculated by mv 2/2/t 2/T. If it is an engineering problem, more problems need to be considered, such as mechanical efficiency, friction must not be ignored, and relevant manuals need to be consulted to calculate.

This mainly depends on how elastic your rope is. Good elasticity will lead to long contact time. Of course, the tension of the rope is small and it is not easy to cut the rope. There is also the strength of the rope. If you want to calculate the required speed, you need to know this, and the result may be very different from the actual situation. But on this issue, it is generally believed that momentum is conservative, because time is short and force is relatively large. Of course, if you feel that it is not accurate enough, you can use some methods to correct the results. These methods can be theoretical deduction or experience summary. This is the engineering solution to the problem.