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Copyright of Caderno Brasileiro de Ensino de Física is the property of Caderno Brasileiro de Ensino de Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Caderno Brasileiro de Ensino de Física is the property of Caderno Brasileiro de Ensino de Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Caderno Brasileiro de Ensino de Física is the property of Caderno Brasileiro de Ensino de Fisica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper shows that it is possible to understand the key features of the gravitational waves emitted by coalescing binary systems from the concepts of fundamental physics. We utilize no more then the contents typically covered in introductory courses on mechanics and electromagnetism that are common to all STEM undergraduate programs. We meticulously deduce the equations required to comprehend the results announced in the paper by the LIGO Collaboration for the event GW150914. Our quantitative description is at least of order of magnitude accurate. We estimate the chirp mass of the coalescing black holes, the total mass of the system, the individual black hole masses, the size of the binary system, and the distance from the Earth to the black holes of the event GW150914. These estimates are performed by utilizing the available data for the amplitude of the gravitational waves, the frequency at the beginning of the inspiral phase, the chirp frequency, and the time until coalescence. In order to illustrate the power of our approach, we apply our quantitative analysis to the first ten gravitational waves detections announced by the LIGO-Virgo Collaboration from February 12, 2016 (discovery event) until June 20, 2020 (event GW190814). [ABSTRACT FROM AUTHOR]

Carathéodory's formalism for classical thermodynamics is a rich alternative approach to this theory, although unpopular with students and physics professors. This approach dispenses with the content of thermal machines for the presentation of the second law of thermodynamics. In this paper, we discuss Carathéodory's formalism historically, and show how Carathéodory's axiom of the second law of thermodynamics is derived, didactically, from the Clausius principle and the Kelvin principle. In addition, also providing an objective character for this paper, in the sense of seeking to popularize the teaching of Carathéodory's formalism in disciplines of classical thermodynamics at undergraduate level, we guide the reader to obtain the entropy and mathematical content of the second law of thermodynamics through this formalism. Finally, considering the wide reviewed literature, the proof we gave for deducing the Carathéodory's axiom of the second law of thermodynamics from the Clausius principle is new. [ABSTRACT FROM AUTHOR]

In this paper we present an analysis of the asymptotic behavior of damped and forced harmonic oscillators considering the (x², x²) representation, we find that from the analysis of the asymptotic behavior of boundary conditions, taking as an example the case of damped and forced harmonic oscillators, which its possible infer the dynamical behavior in this region for more complex systems, such as the nonlinear oscillator described in section 5.Some implications of the asymptotic solution for this system are discussed at the end of this section. However, a more detailed analysis of the analytical behavior of this system would be beyond the scope of this paper. [ABSTRACT FROM AUTHOR]

In this paper, we propose to establish a generalized function for the angular deviation in a prism with a triangular base immersed in different external media. After obtaining such a function, we demonstrate the minimum deviation conditions. In addition, we make a detailed analysis of the function, including the necessary conditions so that there is no total reflection in the interfaces, these conditions that relate to the domain of such a function. In addition, we point out that certain aspects of symmetry existing in the particular case of identical external means are not true for the general case; aspects that, combining the physical principle of reversibility and the mathematical principle of non-contradiction, allow obtaining the angles related to the minimum deviation without the use of differential calculus. [ABSTRACT FROM AUTHOR]

In this paper, we make a complete revision about Nöther's theorems: The one which refers to the global symmetries, the theorem referring to the local ones, and the corresponding reciprocal theorems. We exemplify these theorems by applying them to a variety of situations. Particularly, we show, through the example of Kepler's problem, that the first reciprocal Nöther's theorem finds its maximal applicability only in the Hamiltonian formalism in which the dynamical symmetries are realizable. Finally, we expose the relation between Nöther's energy-momentum tensor and the metric one. We complement the information by treating, in appendix, Lévy-Leblond-Jackiw's formulation that intends to unify the two theorems. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the motion of a falling Slinky, starting from rest and initially suspended from one of its ends. It is well-known that under these conditions, the Slinky moves in an unusual way: its lower end remains at rest until the upper end collides with it - as if gravity were being challenged! We conducted a literature review and identified that the most widely disseminated explanation for this levitation phenomenon of the Slinky's base during the Slinky's fall relies on the concept of information (and does not seem to please many). We show that such a phenomenon can be explained - and reproduced through a computer simulation using a simple model - without the notion that "there is a finite time for the information that the Slinky was released at its top to reach its bottom". [ABSTRACT FROM AUTHOR]

Physics courses are traditionally known for having high dropout and failure rates. In this paper, drawing on Pierre Bourdieu's Sociology of Education, we analyze the relationship between academic performance and dropout in the Physics undergraduate course offered by Federal Institute of Rio Grande do Sul (IFRS), campus Bento Gonçalves. The data indicate that failure in Physics 1 and Calculus 1 (due to lack of attendance or poor performance) favors dropout, while passing the course contributes to students' permanence. On the other hand, it was possible to identify approved students who abandoned the course and failed students who remained. We hope that these results contribute to thinking about the effects of academic evaluations on student retention. [ABSTRACT FROM AUTHOR]

This paper presents and analyzes the methodology for teaching the concept of entropy supported by a science fiction text. In previous publications, we have presented ways of articulating Ausubel's Meaningful Learning and Matthew Lipman's Education theories, the object of his Philosophy Program. We show how this articulation considers the prerogatives of meaningful learning, linking it to higher-order thinking established by research communities and suggesting aggregating methods. As a theoretical-methodological expansion of these references, we transferred the notion of didactic transposition, via science fiction texts, to reinforce these postulates about teaching and cognition. The translational research involved researchers from the field of Physics teaching and 58 second-year high school students from a public institution. In the pedagogical mediation, as a basis for the discussion of the concept of entropy in the Second Law of Thermodynamics, we use one of the most acclaimed short stories by the popular Russian-American author, Isaac Asimov, entitled "The Last Question". For data analysis, we resorted to techniques of semantic frequency and medium order of evocation as constructs of a taxonomy for the investigation of social representations arising from the implemented proposition. The results indicated consistency with the perspective of meaningful learning, consolidating reflections for similar interventions and contiguous research. [ABSTRACT FROM AUTHOR]

The magnetic cannon (Gauss cannon or Gauss rifle) experiment is notable for its cross-disciplinary nature within relevant physics concepts. It is simple, quick, and easy to execute, with a rich supply of mechanics and magnetism to be observed. It has an easy-to-use structure made of a few steel spheres positioned linearly on a rail. Taking these advantages into account, this paper presents a theoretical and experimental study of the Gauss cannon for classroom application using magnetism, kinematics, and energy and momentum conservation principles. The development was based on educational models of energy conservation in the Gauss cannon and was expanded to present a model that uses the principles of linear energy conservation and the potential energy of the magnets. The end result was the acquisition of an ejection velocity equation that could be tested experimentally. It was capable of accommodating more sphere configurations than the two works observed in the literature, and furthermore, it presents a more accurate values. [ABSTRACT FROM AUTHOR]

We present the second part of a series of papers proposing a novel teaching sequence for Particle Physics in high school. The topic of the present work is Nuclear Physics. The goal of the sequence is to approach the subject in a way as to stimulate scientific literacy, from a perspective involving Science, Technology, Society and Environment (STSE). We evaluate the potentialities and effectiveness of the material proposed here, allied to a dialogical approach by the teacher, by analyzing the presence of scientific literacy and engagement indicators during interventions applied at a public school in Espírito Santo, Brazil. [ABSTRACT FROM AUTHOR]

In this paper we describe one of the most promising platforms for the construction of a universal quantum computer, which consists of a chain of N ions trapped in a harmonic potential, whose internal states work out as qubits, and are coupled to collective vibrational modes of the chain. From such coupling, it is possible to build interactions between different ions of the chain, that is, qubit-qubit interactions that, together with individual operations on the ions, allow building a quantum computer as first proposed by Cirac and Zoller in the 1990s [Phys. Rev. Lett. 74, 4091 (1995)]. Here we discuss from the physics involved in trapping ions in electromagnetic potentials to the Hamiltonian engineering needed to generate a universal set of logic gates, fundamental for the execution of more complex quantum algorithms. Finally, we present the current state of the art of quantum computing in trapped ion systems, highlighting recent advances made by companies and government projects that use such architecture, such as IonQ and AQTION. [ABSTRACT FROM AUTHOR]

This work presents some aspects of diffraction in the human eye, which occurs in the pupil, in the cells of the lens, and in structures within it. An Appendix presents the calculations necessary to understand the phenomenon of diffraction. To complement the understanding of optical phenomena, some physiological aspects of the eye, especially the retina, are examined. The purpose of the paper is to provide teachers and students with examples that can help in the study of optics and motivate students to take a closer look at diffraction, including numerical calculations. Examples include the visibility of structures like the Great Wall of China when viewed from long distances, the dots of the letters i and j from the drug information leaflet the shape of floaters, and why we see stars as pointy objects. This article targets physicists, physics students, and professionals from other areas related to human vision, such as ophthalmologists, opticians, and optometrists. [ABSTRACT FROM AUTHOR]

This work aims to make an introduction to the study of a quantum system of a charged particle immersed in a constant magnetic field. First of all, this work starts by recovering some basic concepts of Quantum Mechanics: as Schrödinger equation and Heisenberg equation, time evolution of states, states and operators in position space. This review is a step of the work that complements the next one: the construction of the essential tools for the study of the interaction of a charged particle under the action of a constant magnetic field. Finally, we present the main objective of the paper, which is to show that the study of this interaction, in the Schrödinger wave quantum mechanics formalism, can be realized through Landau levels and the Aharonov-Bohm effect. [ABSTRACT FROM AUTHOR]

Undergraduate Physics courses has one of the highest dropout rates in Brazilian universities. To face this problem, it is necessary a deep understanding of the causes that lead students to withdraw or persist in their undergraduate courses. Despite empirical research, the validation of a theoretical model that explains dropout and student persistence in the Brazilian context is a current challenge for researchers in the field. In this paper, we evaluate the suitability of the Tinto's Persistence Motivation Model, developed in the United States of America, to represent the scenario of an undergraduate Physics course at a Brazilian public university. We carried out a quantitative study from data collected with a questionnaire answered by 168 undergraduate students. The questionnaire brings up statements related to the predictors of student persistence according to the Tinto model (academic self-efficacy, sense of belonging and perception of curricular relevance) and the self-declared intention of persistence. Statistically significant correlations were identified between all constructs, endorsing the theory proposed by Tinto. The linear regression model was able to predict 37% of the variance of intention to persist. This indicates that the model partially represents the investigated setting. New studies must be done to identify other aspects that impact student persistence in the investigated context. [ABSTRACT FROM AUTHOR]

This paper sets out to present, in a brief and intuitive way, fundamental aspects on the construction and formulation of the Yang-Mills-Shaw Theory. Starting off from the paradigm of Maxwell Electromagnetism, we build up, by analogy, the formulation for nonabelian vector fields and their (gauge) interactions with matter. In order to do so, we extend U(1) to the SU(.V) group and write down the nonabelian extension of the Maxwell equations by now defining the electric and magnetic fields for the SU(.V)-symmetry. [ABSTRACT FROM AUTHOR]

Hooke's law establishes a direct relationship between the applied force and deformation triggered on an object, with the elastic constant being the proportionality factor. Introductory Physics courses usually address Hooke's law in the context of real springs. This paper proposes a complementary didactic approach to the topic "elasticity of materials", considering a microscopic model in wich the interatomic bonding behave like springs. Thus, the elastic constant of these structures can be predicted by an extremely simple closed formula in the case of periodic systems. Particularly, monolayer hexagonal boron nitride structures were modeled from a series-parallel combination of identical springs. The model was developed within the linear approach of elasticity to ensure theoretical simplicity. A study was conducted to establish an optimal value corresponding to this regime, and 1.8% was determined as the maximum strain. The model was tested via atomistic computational simulations, being able to accurately predict the values of the elastic constants of the structures. Finally, the proposed approach proved to be didactically simple and interesting in introductory Physics or Engineering courses, mainly for the confirmation of the validity of the usual rules of spring combination in the microscopic domain. [ABSTRACT FROM AUTHOR]

In this paper, we approach different ways to use optical transformation matrices, or ABCD matrices, and optical simulations as tools for teaching geometrical optics. The work presented here ranges from simple situations, such as perfect flat lenses, to more complex situations, such as optical systems in media with different refractive indices. These examples can be easily solved with the use of optical matrices, a powerful tool, yet not widespread in undergraduate physics courses in the country. We will compare results from the classical equations for thin lenses and the matrix method with the results obtained through simulation with the freeware software OSLO EDU to show the power of the matrix method. With this proposal, the teacher will have new ways of approaching the problem and will facilitate both his didactics and student learning in the classroom or optical laboratories. Approaching geometrical optics in a different way will also enable real-world applications and the introduction of optical simulation software in the classroom. [ABSTRACT FROM AUTHOR]

In this paper, we present the elaboration process of an instructional unity consisting of classes using videos, experiments, exercises, tests, and lectures including questions or examples about practical situations, to illustrate theoretical discussions about thermodynamics and fluid mechanics, oriented to environmental and sanitary engineering. The theoretical frame adopted was the educational theory of Dewey, who defends the development of the student's reasoning and critical thinking. The methodology involved data collection through questionnaires, applied to students and professionals from environmental and sanitary engineering, orienting the choice of activities in the context of their professional field to compose the instructional unity. The application of the activities took place during physics classes for second-year students in the environmental and sanitary engineering of a private university. The results indicated an increase in the students' interest, measured by their intense interaction with the experiments and engagement in the discussions. The analysis of the student's answers to an evaluation questionnaire shows that they valued the experience and recommended it for other courses or subjects. [ABSTRACT FROM AUTHOR]

The paper analyzes the production of meanings by students of an undergraduate course in physics, in relation to historical, epistemological and conceptual aspects of the universal gravitation, based on a non-traditional activity in the discipline of Physics Teaching Practices I, in a public university in São Paulo. The activity included watching a video, addressing Theory of Universal Gravitation and its application in understanding the movement of the moon around Earth. The students responded an open questionnaire. The research was developed based on assumptions from the French Discourse Analysis. The articulated approach of historical and conceptual aspects, using graphic resources, made the video attractive, aspects highlighted by the students, showing its potential as a didactic resource. Significant learning was obtained through the manifestation of historical repetitions. It was found that the treatment of epistemological aspects and the history of science provided adequate notions about the nature of science. It was possible to work on conceptual aspects both qualitatively and quantitatively, with indications that students are able to solve quantitative problems and exercises without being submitted to a traditional expository class. As the investigation took place during the pandemic scenario, it was necessary to carry out all school period in remote mode. [ABSTRACT FROM AUTHOR]

The incorporation of discussions about the nature of scientific knowledge in science teaching activities is a fundamental and quite challenging aspect. This paper aims to present an empirical contrast of theoretical models exploring the particular case of the movement of bodies with variable mass as a way to highlight the role of the scientific modeling process in an experimental situation. We investigate the implications of assuming certain idealizations in the contrasted models, explaining the representative character of scientific knowledge in the development of experimental investigations, incorporating the influence of different resistive forces on these bodies, such as air drag forces and rolling resistance. Thus, we seek to expose an example of a situation with the potential to be explored by teachers in overcoming naive epistemological conceptions by students. Also, the investigation involves the use of open-source computational resources in the construction of numerical solutions of theoretical models and the collection of experimental data, favoring the use of free technologies in physics teaching. Four of the six empirically contrasted theoretical models also had their analytical solutions deduced and compared with their respective numerical solutions. The results show that the choice of the best theoretical model that represents the collected data involves more than the analysis of the quality of the adjustment of the models because it demands an evaluation of the hypotheses assumed in the theoretical models and the decisions made by the researcher. [ABSTRACT FROM AUTHOR]

In this paper we will present a portables experiments in order to approach the concepts of electromagnetic induction to Basic Education students. The materials used to perform the experiments are easy to acquire, and the set of them can be purchased in the form of an experimental kit, easily transportable. The proposal is that students learn the concepts through classroom discussion and the execution of experiments, with greater emphasis on interactive classes over lectures. For this, we were inspired by the methodology developed by the group from Rutgers University, led by Professor Eugenia Etkina. The foundation of this proposal is that student's study and learn physical concepts similar to the way scientists work to setup scientific knowledge. Such methodology was called "Investigative Science Learning Environment" (ISLE). In this method, students are introduced to the scientific method, in high school, in a concrete way where observation, proposition and refutation of hypotheses are fundamental for creating a model for the physical phenomenon studied. To evaluate the methodology and use of the portable experiment, we present a proposal for a didactic sequence to be applied to a twelve-year high school class. [ABSTRACT FROM AUTHOR]

This paper presents the "Thermometry", a remotely controlled experiment. We discuss the aspects of the project according to its main areas of development, i.e. the physical structure of the experiment, hardware, and software. The theoretical model for determining the coefficient of linear expansion is discussed in detail. The determination of the coefficient of linear expansion has shown a relative deviation up to 7%, in the module, for heating times equal to or lower than 3 seconds, lowering down to 2% for times equal to 1 second. For values greater than 3 seconds howbeit, these deviations assume significant values, reaching up to 75% for heating times of 10 seconds. Based on these results, some improvements could be drafted, for example, putting the experiment inside an isolated container in order to mitigate the effect of drafts in the lab, lowering thus the environment's thermal conductivity, and enhancing the accuracy of the temperature measurements. These enhancements are to be implemented in the future. From the didactic point of view, the experiment allows a variety of approaches for many different educational levels. Some remarks are presented on this matter. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present Ptolemy's lunar theory in the Almagest. In order to describe the complex Moon's motion, he proposes an intricate system formed by mathematical objects common to astronomers of his time, such as epicycles, deferents and eccentrics. From his lunar theory, Ptolemy determined with good precision the ecliptic longitude and latitude of the Moon relative to the center of the Earth. He also set out to determine the distance from Earth to the Moon, having first to determine the lunar parallax. Although he was relatively successful in describing the Moon's position, his calculations of the distances from Earth to the Moon were not correct, mainly because his lunar model was not a good representation of the Moon's motion. [ABSTRACT FROM AUTHOR]

In this paper, we present Gibbs' original discussion on the equivalence between equilibrium conditions, i.e., a maximum entropy condition for a given energy and the minimum energy condition for a given entropy - which are presented as theorems by the author. Next, we show how such a discussion appears in contemporary textbooks that present Thermodynamics from its laws (law zero plus the three laws). We compare this presentation with the discussion made by Callen, in his postulational approach to Thermodynamics. We show that part of Gibbs' discussion has been lost even in textbooks dealing with the laws. Furthermore, we argue that Callen's approach does not emphasize the fact that although the principles are the same, thermalizing a system composed of distinct processes (one with constant energy and the other with constant temperature) leads to different temperature values. In addition to solving the problem analytically, we present a graphical analysis of the problem. At the end, we discuss implications for thermodynamics teaching. [ABSTRACT FROM AUTHOR]

In this paper, the expression of the relativistic Maxwell-Jüttner velocity distribution was deduced in a detailed and didactic way. This distribution was compared with the well-known Maxwell-Boltzmann distribution, which does not take into account relativistic effects. Applications and comparisons between the two distributions were carried out in three situations: i) protons at solar surface temperature, ii) electrons at Lawson's criterion temperature, and iii) protons at quasar temperature. It was found that the value of the ratio between the rest mass of the particle considered and the temperature of the system determines the need to consider or not a relativistic treatment for the velocity distribution function of the system. [ABSTRACT FROM AUTHOR]

The tight-binding model is a cornerstone of Condensed Matter Physics, describing in a simple way a wide range of phenomena, such as the band structure of materials and the electronic transport. In this paper, the referred model, written in the language of second quantization, is used to describe the density of states in organic polymers. Using the second quantization method the expressions for the hopping parameters emerge quite naturally. The infinite atomic chain, the benzene, cyclopentadiene and tyophene molecules are analyzed within the tight-binding model. [ABSTRACT FROM AUTHOR]

This paper focuses on studying electron-positron scattering. Using the postulates of quantum mechanics, scattering theory and Green's functions, the shape of the S-matrix and its relation to cross sections is shown. In addition, some Feynman rules are presented that are used to find the cross section of an electron-positron scattering that results in a muon-antimuon pair and also the cross section of the same scattering process, but with the outcome of two photons. The technique is also used to write the cross sections of some Higgs boson production processes, such as the Higgs-strahlung and the WW fusion. Finally it is presented a short text on the ILC and CLIC programs and their relation to new physics. [ABSTRACT FROM AUTHOR]

The announcement of a quantum computer that can be accessed remotely by anyone from its laptop is a big event for the quantum computation scientist. In this work we present the International Business Machines (IBM) quantum computer and its platform IBM Quantum Experience (IBM-QE) as a didactic proposal in quantum computation and information. In addition we also consider this paper as scientific divulgation of the IMB advertisement. In this paper we show the main tool (quantum gates) present in the IBM-QE and, through a simple strategy, we discuss about a possible decoherence source in the IBM 5 q-bit chips. As an example of application of our study, we show how to implement the quantum teleportation using the IBM-QE. [ABSTRACT FROM AUTHOR]

In this paper we analyse the mass center and the postural stability of four basic Kung Fu Pak Hok postures. Although biomechanics arose in 60's, its application in martial arts such as Kung Fu, isn't often. There are few case studies which accounts the movements of Kung Fu, however there are none based on the study of its mass center and stability of its basic postures. This paper has as objective to describe the mass center and the stability of each of the four most basic postures of the Kung Fu Pak Hok using the image analytical method in a way that is possible to assemble Physics and Sports in an educational context. In order to calculate the mass center of each posture, it was carried out the image analytical method. The stability calculation was carried out by means of the equilibrium concept associated to the torques generated by the weight force and a destabilizing force. The mass center for each of the four postures was about the belly button. Also, it was noticed that the most stable postures were associated to defensive stances while unstable postures were associated to offensive stances. Nevertheless, the quantitative analysis stand on tune with the qualitative approach linked to the cultural background in the Kung Fu martial art. [ABSTRACT FROM AUTHOR]

In this paper a general classification of representations of the Dirac equation in 1+1 dimensions is described. There are considered such representations in which every Dirac matrix ß, a is associated with a unique Pauli matrix. The classification includes 24 representations among which six representations are main and others are ones with sign modified Pauli matrices. The unitary transformations between all the representations are determined in the explicit form. The study of structure of the set of transformations results in conclusions that all the representations are equivalent, so that anyone of the representations can be obtained from any other by a unitary transformation. It is established that the set of the transformations forms a non-abelian group in respect of matrix product in equivalence classes, which are defined through indistinguishability of transformations, which differ by a phase factor. The group possesses one non-trivial subgroup, which in its turn includes two non-trivial subgroups. The most general form of the Dirac matrices in 1+1 dimensions determined by three arbitrary parameters is presented. Isomorphism of the couple of the Dirac matrices to the couple of orthogonal unitary vectors is demonstrated. Applications of the results obtained in the paper are presented. [ABSTRACT FROM AUTHOR]

In this work we present a low-cost activity that aims to investigate the drag force, which acts on the geometry of a disc, through the damped oscillations of a mass-spring system. Using cardboard disks of different radii and controlling the mass of the oscillatory system, keeping it fixed, we studied the influence of the exclusive variation of the magnitude of the drag force on the dynamics of this system, by varying the radius of the disk, keeping all the others fixed system accessible parameters. The video analysis technique is used to track the movement of the system, leading the student to investigate and draw conclusions about the functional dependence of the viscous frictional force with the radius of the disk, as well as to obtain the spring elastic constant and an estimate for the thickness of the disks. [ABSTRACT FROM AUTHOR]

In solving classical mechanics problems many times we are guided by a feeling of familiarity and analogies. Nevertheless, not always this a good strategy. This is the case of the problem of two masses in free fall in a uniform field which we discuss in this paper. [ABSTRACT FROM AUTHOR]

In this paper we present an acquisition system of time intervals and estimates of velocity by infrared light sensors connected to Arduíno board. Because of precision in time measurements, which present uncertainty in time on the order of 10-4s, we are able to determine the damping ratio for pendulum produced by air friction in a small angles regime. We studied the physical system formed by a small glass bottle suspended by a wire. This system was modeled as different pendulum kinds, e. g., compound pendulum, simple pendulum and damped pendulum, where we discuss about validity limits of these models. [ABSTRACT FROM AUTHOR]

In this work we show how a low cost digital scale and some simple devices such as beaker, support, wires, cord, plastic bag and water can be used to measure the density of solids and liquids. The proposed mounting can be done simply, quickly and cheaply. The physical principles used and the mathematical equations involved are presented in a simple and didactic way, what makes it possible to use the ideas presented in different environments such as classrooms, teaching laboratories or even at home. Despite the simplicity, the precision and accuracy of the measurements are not lost. As an example, we illustrate its use in determining the density of various materials. [ABSTRACT FROM AUTHOR]

This paper sets out to present, in a brief and intuitive way, fundamental aspects of group theory, establishing its relation with the idea of symmetry, drawing a parallel with the development of quantum mechanics and particle physics. We try to approach this topic, which is frequently neglected in undergraduate courses, always starting from the concept of invariance of a given quantity of interest to, only after that, introduce the idea of a symmetry group. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the students' perception of a blended learning experience, designed, and applied in the basic disciplines of Physics 1 of 18 different courses at the University of Brasilia. An opinion survey, using a Likert-type scale, was designed, and used to assess the students' agreement degree with affirmative propositions related to the organization, learning potential, and quality of the evaluation system. The results showed good agreement with the presented propositions, and the importance of the positive role of the online forums in the learning process by promote student-student and student-monitor dialogic interaction. However, it also pointed out some needs, such as (a) interventions that can stimulate the inclusion of less proficient students; (b) activities that can influence this students on developing learning motivation; and (c) reflections on the rules of formative and summative assessments, transforming their punitive aspect into a mediation form in the composition of students' final grades. [ABSTRACT FROM AUTHOR]

The incorporation of discussions about the nature of scientific knowledge in science teaching activities is a fundamental and quite challenging aspect. This paper aims to present an empirical contrast of theoretical models exploring the particular case of the movement of bodies with variable mass as a way to highlight the role of the scientific modeling process in an experimental situation. We investigate the implications of assuming certain idealizations in the contrasted models, explaining the representative character of scientific knowledge in the development of experimental investigations, incorporating the influence of different resistive forces on these bodies, such as air drag forces and rolling resistance. Thus, we seek to expose an example of a situation with the potential to be explored by teachers in overcoming naive epistemological conceptions by students. Also, the investigation involves the use of open-source computational resources in the construction of numerical solutions of theoretical models and the collection of experimental data, favoring the use of free technologies in physics teaching. Four of the six empirically contrasted theoretical models also had their analytical solutions deduced and compared with their respective numerical solutions. The results show that the choice of the best theoretical model that represents the collected data involves more than the analysis of the quality of the adjustment of the models because it demands an evaluation of the hypotheses assumed in the theoretical models and the decisions made by the researcher. [ABSTRACT FROM AUTHOR]

In this paper, we will celebrate the International Year of Light telling a history about the concept of photon in the second half of the twentieth century. One can think that the concept of photon was established in physics just after the 1930s. However, we will highlight that after the 1950s theoretical and experimental developments contributed to revisit the canonical concept of photon of the old quantum theory. In quantum optics, the photon is not represented by the schizophrenic image of individual particle, but rather by a mathematical tool that describes an excitation of a quantum state. This paper dedicates to reveal the ways that led to a sophisticated concept of the photon, passing through the HBT effect, Glauber's coherent states, and ending with the experiments that brought to the fore the quantum nature of light. [ABSTRACT FROM AUTHOR]

This paper aims to show the essential aspects of the development of the physical concept of energy, in order to subsidize the choice of teachers about the best way to understand and teach this concept. We will study the thought of some of the main scientists who were interested on the subject, and the emerging debates around this topic. The paper is divided in two parts. Firstly, some contributions of Thomas Young, Johann Bernoulli, Galileo Galilei, René Descartes and Leibniz will be analyzed. Moreover, the evolution of the physical concept of energy in the context of machines and beyond the mechanics will be presented. The main idea that guides the discussion of this text is the fact that the development of the physical concept of energy is closely related to the development of the principle that there is a "constancy in the midst of change". That is, something is always constant despite changes in the environment. [ABSTRACT FROM AUTHOR]

In this paper, a sum rule for electron transitions between atomic states, proposed by Thomas, Reiche and Kuhn (TRK), presented only, and at most, in advanced courses, is examined in a didactic way for the case of transitions between states of electrons in two familiar systems, the one-dimensional finite and infinite potential wells, traditionally studied in introductory disciplines of quantum mechanics in undergraduate physics courses. [ABSTRACT FROM AUTHOR]

In this paper indirect measurements of the sizes of some lunar craters as well as their selenographic coordinates from lunar surface photographs were performed. In order to carry out the analysis of the images a software was developed in Visual Basic, which is so called Îasy. Comparing the results obtained through the program developed with data provided by an astronomical observatory average percentage deviations of less than 1% were obtained. In view of the didactic potential of the tool capable of reducing abstractions and producing motivation, as well as the reliability of the obtained results, we can verify that Îasy software can be used as an educational tool, as well as assist amateur astronomers in the development of good precision. [ABSTRACT FROM AUTHOR]

Could the world-famous fidget spinner toy be used in the classroom to illustrate the concepts of moment of inertia, torque and angular momentum? Curiously, there are very few papers related to the topic that have been published so far. In this work, we present a real situation consisting of two extremely simple experimental configurations of oblique launching of a spinner with and without initial spin type rotation. We define spin type rotation as any rotation in which the spinner rotates around one of its main symmetry axes. The technique chosen for data collection was the video analysis, using the free software Tracker. The main results were (i) To present a fast and easy execution experiment that simultaneously approaches the concepts of torque, orbital angular momentum and spin angular momentum. (ii) Analyze in a qualitative way the similarities and differences between the orientations of the orbital and spin angular momenta for two types of oblique launching (iii) Obtain a quantitative estimative of the magnitudes of the spin angular momenta in relation to the respective symmetry axis of the spinner, in both cases. [ABSTRACT FROM AUTHOR]

In this paper we present a theoretical study of the physical limits associated with a fundamental particle, the photon, in the Planck scale. In addition, we calculated the temperature of a black hole with Planck dimensions. From the dimensional analysis, we verified five units of the Planck scale (mass, time, length, energy, and temperature). First, we analyze a photon with dimensions of Planck length; Then we identify the energy of this photon with the wavelength of the order of the Schwarzschild ray (rs). Finally, we calculate the temperature of a black hole with Planck's dimensions (in this case, with its Schwarzschild radius equal to the Planck's length). The “photon ray� appears as a multiple of Planck's length, demonstrating the inaccessibility of scales smaller than Planck's due to the Uncertainty Principle. Among the results obtained, we can highlight three possible paths to the Planck scale, as well as the smallest possible photon measurement according to the laws of physics, which is characterized by maximum frequency and energy. [ABSTRACT FROM AUTHOR]

Black holes are arguably the most counter-intuitive consequence of general relativity. They are super dense objects surrounded by unidirectional membranes, each hiding a singularity inside. A black hole traps everything that enters it, including light. The history of the discovery of those enigmatic objects starts in 1916, with the first solution to Einstein's Equations for the gravitational field of a massive spherical-symmetric dimensionless body. But the publication that introduced them appeared only in 1939. This paper presents the historical events of the initial phase of research that led to the rise of the black holes as a concept. It presents a social, philosophical, and political analysis of the subject. [ABSTRACT FROM AUTHOR]

In this paper we present a set of didactic activities (DA) of Physics, mediated by hypermedia educational resources, that approach electrical energy in homes, relating Physics contents from Electrodynamics. For this, we consider the importance to recontextualize scientific knowledge - explained by several authors and by the official documents aimed at the high school of Physics - that allows students deal with the situations they experience or may experience, many of them new and original. In this context, the DA were structured with the theoretical-methodological basis of the Cognitive Flexibility Theory (CFT), that emphasizes the development of cognitive flexibility (CF) as essential in the construction, organization and restructuring of knowledge in the face of new situations and contexts of use. Throughout the text, we describe the steps related in the planning of activities, as well as analyzing the advances and obstacles in structuring them in accordance with the assumptions of the TFC. The potentialities of DA are also discussed, with an emphasis on their contribution to the development of CF within the scope of high school. [ABSTRACT FROM AUTHOR]

â€Origins of life in the cosmic context†was the first one Astronomy MOOC in Portuguese-language. The launch took place in June 2016, initially counting more than 4,000 students, which gradually (and cumulatively) until the last session analyzed (august, 2019). This paper shows the MOOC methodology that already attended more than 150 thousands students and a discussion about the maintenance in a mentored and independent way. As a result, we found that the course completion rate was around 9%, which corroborates the literature, in addition to the predominance of higher education students and males. The students satisfaction level was high: on a scale of 0 to 5, satisfaction was assessed at 4.8. Moreover, the course has already transcended the virtual world barrier and have been used as a tool to aid astronomy learning in elementary and middle schools. [ABSTRACT FROM AUTHOR]

In this paper, we developed the theoretical model Cooke triplet in an environment that runs programs quickly; which means you can build surfaces; increasing them and solving more complex and elaborated designs. This result is compared with the optical device developed with OSLO EDU [1] software. We show how a simple code is presented as a computational tool for the teaching of geometric and paraxial optics of the first order for an introductory optics course. [ABSTRACT FROM AUTHOR]