Particles don't actually exist. Particles are points with mass but no volume and shape, and they are idealized models of physics. When the size and shape of an object don't work, or the role it plays is not significant, it can be ignored. We approximately regard this object as an ideal object with only mass, and its volume and shape can be ignored. The point with mass used to replace this object is called a particle.

Extended data

Particle model

In the mechanical model, particles and rigid bodies constitute the non-deformable body model (theoretical mechanics), and the corresponding typical structural models in the deformable body model include rods, columns, beams, shafts (material mechanics), trusses, frames (structural mechanics), plates and shells (plate and shell structures) and so on. Particle and rigid body models mainly study external force balance, macroscopic motion law of objects, and the relationship between mechanics and motion; Deformation mechanics not only needs to study the external characteristics of objects, but also needs to enter the interior of materials to analyze the strength, stiffness and stability of structures or materials.

Therefore, theoretical mechanics is the basis of all mechanics courses, and particle becomes the simplest mechanical model in mechanics courses, and it is also the basis of rigid body and deformation mechanics. Many mechanical principles, such as velocity synthesis, equilibrium system, collision law, conservation of momentum and energy, are studied under the particle model.

Through the analysis of the concept of particle, this paper puts forward the simplification principle of particle model.

First of all, a "point" mathematically represents a position in space. It has no size or shape. A particle is a point with mass. Particles only occupy space position, not space volume! Particles do not exist in practice, even microscopic particles such as atoms and electrons will have a certain volume, thus occupying a certain space. When analyzing problems, there are three main situations that can be simplified as particle models:

First, the research object is very small relative to its space;

Second, when the motion of each point on an object is completely consistent, it can be simplified as a particle;

Third, according to a certain research goal, it can be simplified as a particle.

References:

Baidu encyclopedia-particles