Name: cutting pliers as a force-multiplying machine
Uploaded: 2023-09-22T11:49:25.000Z
Duration: 1 min 19 s
Channel: JoVE

K12 Standards

Arizona Science Standards

High School

Physical Science

HS.P3

HS.P3U2.7

Machines

Las máquinas son estructuras hechas de miembros móviles de múltiples fuerzas conectadas por clavijas que forman un sistema estabilizado para transmitir fuerzas.
Considere un alicate de corte que se usa para cortar un cable aplicando fuerzas en su mango.
Cuando se aplican fuerzas iguales y opuestas en los mangos del alicate de corte, hace que los bordes de corte del alicate se junten y apliquen fuerzas de reacción iguales y opuestas en el alambre, que son mayores que las fuerzas aplicadas.
La magnitud de las fuerzas ejercidas sobre el alambre debido a las fuerzas aplicadas se puede determinar desmontando el alicate de corte y dibujando un diagrama de cuerpo libre de los componentes del alicate de corte.
Al tomar un momento alrededor del pasador de pivote que mantiene unido el alicate, se puede establecer una relación entre las fuerzas aplicadas y de reacción, que actúan a distancia.
De manera similar, al dibujar un diagrama de cuerpo libre para el pasador de pivote, se pueden determinar los componentes de la fuerza interna en el pasador de pivote.

<ol>
	<li>Hibbeler, R.C. (2016). Ingeniería Mecánica \u2012 Estática y Dinámica. Hoboken, Nueva Jersey: Pearson Prentice Hall. págs. 305</li>
	<li>Cerveza, F.P.; Johnston, E.R.; Mazurek, D.F.; Cromwell, P.J. y Self, B.P. (2019). Mecánica vectorial para ingenieros: estática y dinámica. Nueva York: McGraw-Hill. págs. 107 - 348</li>
</ol>

No se han declarado conflictos de interés.

máquinas

Las máquinas son estructuras complejas que consisten en miembros móviles conectados por pasadores y multi-fuerzas que trabajan juntos para transmitir fuerzas. Un ejemplo de máquina es la tenaza de corte, que se utiliza para cortar alambres aplicando fuerzas en sus mangos. Cuando se ejercen fuerzas iguales y opuestas en los mangos de la tenaza de corte, hacen que los bordes de corte se junten y apliquen fuerzas de reacción iguales y opuestas en el alambre, que son mayores que las fuerzas aplicadas. Se considera un diagrama de cuerpo libre de los componentes de la tenaza de corte para determinar la magnitud de las fuerzas que actúan en el alambre debido a las fuerzas aplicadas. <img alt="Figure 1" src="/files/ftp_upload/14293/14293_PT_Fig_1v2.svg" style="text-align: center; height: 350px;"> Analizar el momento sobre el pasador que mantiene unida la tenaza puede ayudar a establecer una relación directa entre la fuerza aplicada F y la fuerza de reacción P, con respecto a sus distancias respectivas desde el pasador. <img alt="Equation 1" src="/files/ftp_upload/14293/14293_PT_Equation_1v2.svg" style="text-align: center; height: 30px;"> Además, al crear un diagrama de cuerpo libre para el pasador, es posible determinar las componentes de la fuerza interna en el punto de pivotamiento. Aplicando la condición de equilibrio de fuerzas horizontales, la fuerza interna Ox es cero. De manera similar, aplicando la condición de equilibrio de fuerzas verticales, la fuerza interna Oy es igual a la suma de la fuerza aplicada F y la fuerza de reacción P.

Máquinas

Las máquinas son estructuras complejas que constan de miembros móviles de múltiples fuerzas conectados por clavijas que trabajan juntos para transmitir fuerzas. Un ejemplo de una máquina ...

Education

Educación

JoVE Core

Mechanical Engineering

Ingeniería Mecánica

Unit 1

Unidad 1

Structural Analysis

Análisis estructural

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

cutting pliers as a force-multiplying machine

Cutting pliers are a machine that helps transmit force through movable, pin-connected members. In this example, the handles and cutting edges work together to cut wire by turning an input force into a larger output force at the jaws.

When equal and opposite forces are applied to the handles, the cutting edges move toward each other. They then apply equal and opposite reaction forces to the wire. These reaction forces are greater than the forces applied to the handles, which is why the wire can be cut.

A free-body diagram of the plier parts is used to find the size of the forces acting on the wire. Taking the moment about the pivot pin, the pin that holds the pliers together, gives a direct link between the applied force F and the reaction force P. That relationship depends on how far each force acts from the pivot pin.

A free-body diagram of the pivot pin also shows the internal force at that point. Using horizontal force equilibrium, the internal force O x is zero. Using vertical force equilibrium, the internal force O y equals the sum of the applied force F and the reaction force P.

Cutting Pliers as a Force-Multiplying Machine

cutting-pliers-as-a-force-multiplying-machine

introduction to structures

Structure Types and Force Paths

Structures are systems of interconnected members that support or transfer forces and handle the loads placed on them. Engineers can find the internal forces in a structure by breaking it apart and drawing free-body diagrams for individual members or groups of members. This helps show how structural elements behave and how the whole system stays stable under load. There are three main categories of structures: trusses, frames, and machines. Trusses are stationary structures that stay rigid when...

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method of joints

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method of joints: problem solving i

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method of joints: problem solving ii

Truss Force Analysis at Joints A to E

Truss force analysis at joints A to E uses the method of joints to find the force in each member. The truss has frictionless joints, a wall support, and a roller support. A 150 N force is applied at joint A, and the member forces are solved from joint to joint. First, the angle between members AC and AB is found using the inverse tangent of the ratio of BC to AB. This gives an angle of 67.38°. A free-body diagram of joint A is then drawn, and each unknown force is split into vertical and...

zero-force member

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method of sections

Truss Member Force Analysis by Sections

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method of sections: problem solving i

Truss Member Force Calculation by Sections

Truss member forces can be found with the method of sections in a symmetrical roof truss. The structure here includes vertical, diagonal, and horizontal members. Each horizontal member is 4 m long. The vertical members FB and HD are 4 m long, and member GC is 6 m long. The roof truss carries loads at several joints. Joints F, G, and H each have a 2 kN load. Joints A and E each have a 1 kN load. To start the analysis, moment equilibrium is used at point A. The force and distance values are...

method of sections: problem solving ii

Truss member force analysis by sections finds the forces in selected members of a wall-mounted truss. The structure here includes diagonal, vertical, and horizontal members. The known loads and member lengths are used to solve for the forces in CB, GB, and GH. A cut is made through members CB, GB, and GH. The right side of the truss is then isolated as a free-body diagram. Next, the moment equilibrium equation is taken about point G. This step gives the force in member CB as 4 kN, and the...

space trusses

Space Truss Forces and Stability

A space truss is a three-dimensional truss made from members joined at their ends. It is the 3D version of a planar truss. These frameworks often use ball-and-socket joints, which help the structure stay stable and flexible under load. Space trusses are used in many construction projects because they can adapt to complex forces. Their basic building block is the tetrahedron. A tetrahedron has six members and four triangular faces. Engineers can build larger space trusses by adding one joint...

space trusses: problem solving

3D Truss Force Analysis with Joint Equilibrium

A space truss is a three-dimensional truss structure made of members connected at their ends. It often uses ball-and-socket joints to form a stable and versatile framework. Because it can handle complex loads, this type of structure is used in many construction projects. The example begins with a tripod made from a tetrahedral space truss. A ball-and-socket joint is located at C. The height and the lengths of the horizontal and vertical members are known. A tensile force is applied at joint D.

frames

Frame Analysis in Structural Systems

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frames: problem solving i

Jib Crane Reaction Forces in Frames

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frames: problem solving ii

Hydraulic Hoist Force Analysis

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machines

Cutting pliers are a machine that helps transmit force through movable, pin-connected members. In this example, the handles and cutting edges work together to cut wire by turning an input force into a larger output force at the jaws. When equal and opposite forces are applied to the handles, the cutting edges move toward each other. They then apply equal and opposite reaction forces to the wire. These reaction forces are greater than the forces applied to the handles, which is why the wire can...

machines: problem solving i

Toggle Clamp Force Analysis

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machines: problem solving ii

Lifting Tong Force Analysis

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key terms and concepts

See how cutting pliers act as a machine, using a pivot pin, free-body diagrams, and force balance to produce a larger cutting force on wire.

Cutting Pliers as a Force-Multiplying Machine | 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.

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SPS8.

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Cutting Pliers as a Force-Multiplying Machine

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