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

Les machines sont des structures constituées d’éléments multiforces mobiles reliés par des broches qui forment un système stabilisé pour transmettre les forces.
Considérez une pince coupante utilisée pour couper un fil en appliquant des forces sur sa poignée.
Lorsque des forces égales et opposées sont appliquées sur les poignées de la pince coupante, les bords de coupe de la pince se rapprochent et appliquent des forces de réaction égales et opposées sur le fil, qui sont supérieures aux forces appliquées.
L’amplitude des forces exercées sur le fil en raison des forces appliquées peut être déterminée en démontant la pince coupante et en dessinant un schéma à corps libre des composants de la pince coupante.
En prenant un moment sur l’axe de pivot qui maintient la pince ensemble, une relation peut être établie entre les forces appliquées et les forces de réaction, qui agissent à distance.
De même, en dessinant un schéma de corps libre pour l’axe de pivot, les composantes de la force interne au niveau de l’axe de pivot peuvent être déterminées.

<ol>
	<li>Hibbeler, R.C. (2016). Génie mécanique \u2012 Statique et dynamique. Hoboken, New Jersey : Pearson Prentice Hall. p. 305</li>
	<li>Bière, F.P. ; Johnston, E.R. ; Mazurek, D.F ; Cromwell, P.J. et Self, B.P. (2019). Mécanique vectorielle pour les ingénieurs \u2012 Statique et dynamique. New York : McGraw-Hill. pages 107 à 348</li>
</ol>

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les machines

Les machines sont des structures complexes composées d'éléments mobiles reliés entre eux par des pivots et soumis à des forces multiples, qui travaillent ensemble pour transmettre des forces. Un exemple de machine est la pince coupante, qui est utilisée pour couper des fils en appliquant des forces sur ses poignées. Lorsque des forces égales et opposées sont exercées sur les poignées de la pince coupante, elles amènent les bords coupants à se rapprocher et à appliquer des forces de réaction égales et opposées sur le fil, qui sont supérieures aux forces appliquées. Un schéma corporel des composants de la pince coupante est considéré pour déterminer l'ampleur des forces agissant sur le fil en raison des forces appliquées. <img alt="Figure 1" src="/files/ftp_upload/14293/14293_PT_Fig_1v2.svg" style="text-align: center; height: 350px;"> L'analyse du moment autour de l'axe de pivotement qui maintient la pince ensemble peut aider à établir une relation directe entre la force appliquée F et la force de réaction P, par rapport à leurs distances respectives par rapport à l'axe de pivotement. <img alt="Equation 1" src="/files/ftp_upload/14293/14293_PT_Equation_1v2.svg" style="text-align: center; height: 30px;">

De plus, en créant un schéma corporel pour l'axe de pivotement, il est possible de déterminer les composantes de la force interne au point de pivotement. En appliquant la condition d'équilibre des forces horizontales, la force interne O(x) est nulle. De même, en appliquant la condition d'équilibre des forces verticales, la force interne O(y) est égale à la somme de la force appliquée F et de la force de réaction P.

Les machines

Les machines sont des structures complexes composées d’éléments multiforces mobiles et reliés par des broches qui travaillent ensemble pour transmettre des forces. Un exemple de machine ...

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Enseignement

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Mechanical Engineering

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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

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method of sections: problem solving i

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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

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frames

Frame Analysis in Structural Systems

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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...

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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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Cutting Pliers as a Force-Multiplying Machine

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