mechanical equilibrium is a stationary state in which one of these two conditions is met:

The second definition is more general and useful, especially in continuous media mechanics.

Contenido

Como consecuencia de las leyes de la mecánica, una partícula en equilibrio no sufre aceleración lineal ni de rotación, pero puede estar moviéndose a velocidad "Velocidad (física)") uniforme o rotar a velocidad angular uniforme. Esto es ampliable a un sólido rígido.

Necessary condition of equilibrium

The necessary equations of mechanical balance are:.

A rigid solid is in equilibrium if it is in translational and rotational equilibrium.

A particular type of mechanical equilibrium is distinguished called static equilibrium, which would correspond to a situation in which the body is at rest, with zero speed: a sheet of paper on a desk will be in mechanical and static equilibrium, a parachutist falling at a constant speed, given by the limit speed, would be in mechanical but not static equilibrium.

Sufficient conditions

As stated in the previous section, given a solid, a necessary condition for this solid to be in mechanical equilibrium is that the sum of reactions and the moment resulting from these reactions is zero. If the solid is non-deformable, the condition, in addition to being necessary, is sufficient; however, for certain deformable solids, the condition that the sum of forces and moments cancel may not be sufficient. In the latter case, the differential equilibrium equations must also be satisfied locally:

Where:.

The above conditions are also applicable to a fluid and for most fluids the above equations are equivalent to a simpler form.