catenary
Introduction
A catenary is an ideal curve that physically represents the curve generated by a chain "Chain (object)"), rope or cable without flexural rigidity, suspended from its two ends and subjected to a uniform gravitational field. This word comes from the Latin catēnarĭus ('own chain'). The involute of a tractor is a catenary.
History
The catenary problem, raised during the 19th century, consisted of determining the shape that a chain or rope (without flexural rigidity) adopted within a uniform gravitational field. That is, when the rope's own weight acted vertically on a rope segment and was supported simultaneously by the tensions at its ends, in directions tangent to a curve segment at its ends. The first physicists and mathematicians to address the problem assumed that the curve was a parabola "Parabola (mathematics)"), because empirically the shape of the string closely resembles a parabola, especially if small lengths of string are considered. But it was Christiaan Huygens, at age 17, who showed that the curve was not really a parabola, but just a similar curve, although he did not find the equation of the catenary.
The equation was obtained by Gottfried Leibniz, Christiaan Huygens and Johann Bernoulli in 1691, in response to the challenge posed by Jakob Bernoulli. Huygens was the first to use the term catenary in a letter to Leibniz in 1690 and David Gregory wrote, that same year, a treatise on the curve.[1].
Mathematical approach
Contenido
La condición de equilibrio de un cable sometido a su propio peso vertical lleva a un problema de equilibrio en el plano (la catenaria es siempre una curva plana si se puede despreciar la rigidez flexional del cable). De la condición de equilibrio local de cada punto se desprende la siguiente ecuación diferencial para la pendiente de la catenaria, que relaciona las tensiones en los extremos de un tramo y el peso del mismo (ver deducción de la catenaria):.
Donde:.
La solución general viene dada por:.
La solución de la ecuación anterior para un cable suspendido de dos puntos a la misma altura y cuyo punto mínimo es el punto (0,a) resulta ser:.