How can we calculate the quality point?

The movement state of each part is the same during exercise.

It's an ideal way to facilitate physical calculations where there is no such thing as a particle.

Decision theorem: To treat an object as a particle, it is necessary to look at the nature of the problem under study, and not to the object itself. Therefore, whether an object can be considered as a particle needs to meet one of them:

When the size of the object is extremely small compared to the other distances in the problem under study. The motion of the individual parts of an object is the same, and the motion of any point of the object can represent the motion of the whole object.

Under idealized conditions, the conditions that are met are:

1) All points on an object move the same way, which can be regarded as a particle.

2) The size and shape of the object have little impact on the research problem and can be regarded as a particle.

3) The rotating object with the bent potato body, as long as its rotation is not studied and conforms to Article 2, it can also be regarded as a particle.

There are two types of moving objects that can be considered as particles:

1) The shape and size of a moving object are negligible compared to the problem it is studying, such as studying the Earth's revolution around the Sun, and the Earth can be used as a point of mass.

2) For translational objects, one point can be used to represent the motion of the whole object because the motion of each point on the object is the same.

Definition of particles.

A particle is an idealized model, which is a scientific abstraction of an actual object under certain conditions. A particle does not have to be a very small object, as long as the shape and size of the object are irrelevant or secondary factors in the problem being studied, i.e., the shape and size of the object have a very small effect on the problem under study and the object can be considered as a particle.

It focuses on the study of the influence of objects on the system during motion and force, ignoring some complex but unrelated factors. In theoretical mechanics, an object is often abstracted as its center of gravity, especially in statics and kinematics.

The above content refers to Encyclopedia - Mass Point.

The condition for an actual object to be considered a particle: the shape and size of the object have a negligible impact on the research question. Objects in the same motion, in different research questions, can sometimes be regarded as particles, and sometimes they cannot.

1. When the motion of each point in physics is the same (translational), it can be regarded as a particle, and the object cannot be regarded as a particle.

2. When the object rotates, but the rotation of the object is not the main problem we study, the size and shape of the object itself have become secondary factors, and the object can be regarded as a particle.

3. When the size of the object itself cannot be ignored to the problem being studied, the object cannot be regarded as a particle.

4. Whether an object can be regarded as a particle depends on whether its shape and size are negligible in the problem studied, and has nothing to do with the size of the object's own volume, mass and speed.

5. Whether an object can be regarded as a particle depends on the nature of the problem under study, even if the same object can be regarded as a particle in some cases and not in some cases when the research problem is different.

A particle is an abstraction of an object into a point with mass, the shape and volume of which do not need to be studied. Judgment method: When the size and shape of the object do not play a role, or the effect is not significant and negligible, we approximate the object as a particle.

For example, when studying the rotation of the earth, it can be regarded as a particle. Studying rotation is not possible.

To put it simply, some of the data in the digression is too small and too large relative to the distance or something else, you just need to remember that the particle is not a very small object, it is relative. If it is studied in itself, it cannot be regarded as a particle,