A rigid body is one whose shape does not change despite being subjected to the action of external forces. This means that the distance between the different particles that make it up is invariable over time.

The rigid body is an ideal model used for studies of kinematics and mechanics. However, in practice, all bodies deform, albeit minimally, when subjected to the effect of an external force. Therefore, real machines and structures can never be considered absolutely rigid.

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A rigid body is not deformed by external forces.

Kinematics and mechanics

We can establish that kinematics is a scientific branch, specifically framed within the field of physics, which has as its object of study what the movements of bodies are, without taking into consideration what the pressures or forces are that they are seen. subdued.

It is also important to highlight the fact that the aforementioned scientific discipline develops its studies and analyzes having three fundamental pillars for it. These are none other than time, space and mobile. All this gives rise to subsequently working with uniformly accelerated rectilinear motion, simple harmonic motion, rectilinear motion, circular motion or parabolic motion, among others.

Meanwhile, for its part, the aforementioned mechanics also carries out the study of the movement of bodies but also their rest. Two questions in which he does also study what are the forces that act on those.

The study of pulleys is one of the fundamental fields of work within this aforementioned scientific branch that we find with the fact that it in turn has several ramifications. In this way, there is relativistic quantum mechanics, relativistic mechanics, quantum mechanics, and classical mechanics. The latter is divided into two: statistical mechanics and continuum mechanics.

Specifically, the last of all those exposed is the one that focuses on studying in depth what acoustics, deformable solids and fluids are.

Rigid bodies are theoretical constructions: in practice, all bodies undergo some kind of change when influenced by an external force.

Motions of a rigid body

There are different modes of motion of a rigid body. The translation consists of the transfer of the body, so that, at each moment, the particles that form it maintain the same speed and acceleration.

With rotation, the particles move relative to an axis with the same speed and angular acceleration.

When translation and rotation are combined, the general motion appears, which is studied from the translation and rotation of the center of mass.

Specialists often study the effect of the forces exerted on the rigid body to determine how one system of forces can be replaced by an equivalent one that is simpler. For this, they are based on the assumption that the effect of the force remains unchanged as long as the force moves in its line of action, which means that the forces can be represented by slip vectors.

Among the fundamental concepts for these studies are the moment of the force with respect to its axis and the moment of the force with respect to a point, which allow different calculations to be made.