Action-reaction at a distance

Brand, Howard

doi:10.1119/1.1466543

Cited by 5 publications

(1 citation statement)

References 1 publication

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“…A very feasible way to exchange forces between objects is by means of magnetic fields, since they avoid the mechanical contact of the objects and their magnitudes can be con trolled by electric current in solenoids or varying distances between permanent magnets [12][13][14]. A remarkable experiment involves the fall of magnets that reach terminal speed inside elec tric conductive tubes, exchanging forces between them via magnetic fields generated by eddy cur rents [15,16]. Some approaches use familiar objects, like weights and scales, while others use more involved apparatus like frictionless bead tables [11], currentcontrolled solenoids [13,14], digital force probes [12] and Arduino boards [10], just to cite a few.…”

Section: Introductionmentioning

confidence: 99%

A simple and effective magnetic dynamometer to teach Newton’s third law

Scomparin¹,

Carvalho-Neto²

2018

Phys. Educ.

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Newton's laws of mechanics are a cornerstone in the development of modern science and its learning can be the very first opportunity for students defy their common sense perceptions and replace them with a more robust world view. However, despite their fundamental importance, many studies demonstrate how difficult is the true comprehension of the basic aspects of Newton's laws. Therefore, any effort to increase the possibilities of teaching them is welcome. It is in this sense that we propose an experimental apparatus to assist teachers in the specific case of the Newton's actionreaction third law. Our system is formed by a pair of dynamometers made from a flexible plastic strip to where small neodymium magnetic disks are attached. Forces are exchanged by means of the magnetic fields and the plastic strip deflection angle indicates the force magnitudes. This is a very cheap, easy to build and effective arrangement, suitable for numerous classes that demand many experimental kits.

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Section: Introductionmentioning

confidence: 99%

A simple and effective magnetic dynamometer to teach Newton’s third law

Scomparin¹,

Carvalho-Neto²

2018

Phys. Educ.

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How About a Magnet and a Paper Clip?

Pfister

2005

The Physics Teacher

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Physics education research shows that many introductory physics students have difficulties fully grasping Newton's third law.1 This is exacerbated when we ask for the validity of Newton's third law in areas outside of mechanics, such as electrostatics or magnetostatics. Undoubtedly, there is a difference between hearing about something and actually seeing or feeling it. Students can be told that two forces are equal and opposite but this by no means implies that they are convinced this is indeed the case. Some students respond with the correct answer but still harbor a remnant of doubt that the forces might not be the same.

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Magnetic Levitation and Newton's Third Law

Aguilar

2007

The Physics Teacher

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Newton's third law is often misunderstood by students and even their professors, as has already been pointed out in the literature.1,2 Application of the law in the context of electromagnetism can be especially problematic, because the idea that the forces of “action” and “reaction” are equal and opposite independent of the medium through which they act can be muddied by the concept of “action at a distance.” While some experiments have been described3,4 illustrating Newton's third law in magnetic situations, these do not offer the student a clear way of evaluating his/her own preconceptions. The experiment we present shows how easily the student, and even the graduate student, can fail to apply the third law correctly in an electromagnetic situation. The experiment described here employs a magnetic levitator and shows the difficulty in recognizing action and reaction forces.

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Action-reaction at a distance

Abstract: Lenz’s law is used to demonstrate that Newton’s third law includes forces acting at a distance. The action-reaction pair is the force on a magnet falling through a conducting tube at terminal velocity, and a force on the tube.

Cited by 5 publications

References 1 publication

A simple and effective magnetic dynamometer to teach Newton’s third law

A simple and effective magnetic dynamometer to teach Newton’s third law

How About a Magnet and a Paper Clip?

Magnetic Levitation and Newton's Third Law

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