Name: friction’s role in machine efficiency
Uploaded: 2023-09-22T11:49:20.000Z
Duration: 1 min 14 s
Channel: JoVE

La eficiencia mecánica de una máquina es la relación entre la producción y el trabajo de entrada.
Para una máquina ideal, la relación es uno, lo que implica que el trabajo de entrada y salida es igual.
Por ejemplo, en un tornillo de banco ideal que comprime la madera, el trabajo de salida debido a la fuerza de reacción es igual al trabajo de entrada debido a la fuerza aplicada.
Por el contrario, una máquina real experimenta una fuerza de fricción.
La fuerza de fricción se puede obtener a partir de la fuerza de reacción normal.
El trabajo virtual total debido a las fuerzas contribuyentes, cuando se aplica en el principio del trabajo virtual, da el trabajo de salida como la diferencia entre el trabajo de entrada y el trabajo debido a la fuerza de fricción.
Dividir el trabajo de salida por el trabajo de entrada da la eficiencia mecánica. La eficiencia en ausencia de fricción es una. Sin embargo, para un coeficiente de fricción distinto de cero, la eficiencia es cero cuando el ángulo de alternancia es igual al ángulo de fricción y negativo para ángulos de alternancia menores que el ángulo de fricción.
Esto implica que un tornillo de banco debe usarse solo para un ángulo de palanca mayor que el ángulo de fricción.

<ol>
	<li>Beer, F.P., Johnston, E.R., Mazurek, D.F., Cornwell, P.J. y Self, B.P. (2016). Mecánica vectorial para ingenieros. Undécima Edición, Nueva York: McGraw-Hill Education. Págs. 580-581.</li>
</ol>

eficiencia mecánica de las máquinas reales

La eficiencia mecánica de una máquina es un concepto fundamental que describe cómo eficazmente una máquina puede convertir el trabajo de entrada en trabajo de salida. Según este concepto, la eficiencia de una máquina es igual a la relación entre el trabajo de salida y el trabajo de entrada. Una máquina ideal, es decir, una máquina que no tiene pérdidas de energía, tiene una eficiencia de uno. Esto implica que el trabajo de entrada y el trabajo de salida son iguales. Sin embargo, en realidad, ninguna máquina puede ser verdaderamente ideal y todas experimentan algún tipo de pérdida de energía. Una de las fuentes principales de pérdida de energía en las máquinas es la fricción. Por ejemplo, consideremos un tornillo de banco utilizado para comprimir bloques de madera. En ausencia de fricción, el trabajo de salida del tornillo de banco es igual al trabajo de entrada de la fuerza aplicada, lo que lo convierte en una máquina ideal. Sin embargo, en realidad, el bloque deslizante del tornillo de banco experimenta una fuerza de fricción contra el plano horizontal. Para determinar la eficiencia mecánica de un tornillo de banco real, primero se calcula la reacción normal y la fuerza de fricción correspondiente. Luego, se evalúa el trabajo virtual total de todas las fuerzas durante el desplazamiento virtual. Aplicando el principio de trabajo virtual, el trabajo de salida del tornillo de banco resulta ser la diferencia entre el trabajo de entrada y el trabajo de la fuerza de fricción. En consecuencia, se puede calcular la fuerza de reacción neta, que es cero cuando el ángulo del tornillo de banco es igual al ángulo de fricción y negativo cuando es menor que el ángulo de fricción. Esto significa que el tornillo de banco solo debe utilizarse cuando su ángulo supera el ángulo de fricción. La eficiencia mecánica del tornillo de banco en ausencia de fricción es uno. Sin embargo, cuando hay fricción presente, la eficiencia puede volverse cero o menor que uno, dependiendo del coeficiente de fricción. Cuanto menor sea el coeficiente de fricción, más cercana será la eficiencia a uno; por el contrario, cuanto mayor sea el coeficiente de fricción, menor será la eficiencia. La eficiencia mecánica de una máquina es un concepto esencial que explica cómo eficazmente una máquina puede convertir el trabajo de entrada en trabajo de salida. En realidad, ninguna máquina puede ser completamente ideal y todas experimentan algún tipo de pérdida de energía debido a la fricción. Al analizar la eficiencia de una máquina, es crucial considerar los efectos de la fricción y su coeficiente, ya que desempeñan un papel importante en la determinación de la fuerza de reacción neta y la eficiencia general de la máquina. Mientras que una máquina ideal puede lograr una eficiencia perfecta, las máquinas reales siempre tendrán una eficiencia menor que ideal debido a las pérdidas de energía, especialmente por la fricción.

Eficiencia mecánica de las máquinas reales

La eficiencia mecánica de una máquina es un concepto fundamental que describe la eficacia con la que una máquina puede convertir el trabajo de entrada en trabajo de salida. ...

Education

Educación

JoVE Core

Mechanical Engineering

Ingeniería Mecánica

Unit 1

Unidad 1

Virtual Work

Trabajo virtual

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

Mechanical Efficiency of Real Machines

friction’s role in machine efficiency

Mechanical efficiency shows how well a machine turns input work into output work. It is calculated as the ratio of output work to input work. An ideal machine has an efficiency of one, which means the input work equals the output work.

Real machines are never perfectly ideal because some energy is lost. Friction is one of the main causes of that loss. In a toggle vise used to compress wooden blocks, the sliding block rubs against the horizontal plane and creates friction.

To find the efficiency of a real vise, first calculate the normal reaction and the frictional force. Then use the principle of virtual work to evaluate the total virtual work of all the forces during a virtual displacement. With friction present, the output work equals the input work minus the work done by friction.

This analysis also gives the net reaction force. It is zero when the angle of the vise equals the angle of friction. It becomes negative when the angle is smaller than the angle of friction, so the vise should be used only when its angle is greater than the friction angle.

A vise with no friction has an efficiency of one. When friction is present, the efficiency can be less than one or even zero, depending on the coefficient of friction. A lower coefficient of friction gives an efficiency closer to one, while a higher coefficient lowers the efficiency.

Friction’s Role in Machine Efficiency

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mechanical efficiency of real machines

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key terms and concepts

Learn how friction lowers mechanical efficiency in real machines, using a toggle vise example, virtual work, and the angle of friction.

Friction’s Role in Machine Efficiency | JoVE K12

JoVE Core Mechanical Engineering offers concise, easy-to-understand animated videos covering key topics such as equilibrium, forces, truss analysis, and structural mechanics. Explore their real-world applications, and witness these concepts in action through scientist-led experiments.

mechanical engineering

Friction’s Role in Machine Efficiency

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