Contemporary gravimetry uses gravimeters to find the magnitude of gravitational acceleration (g) in a punctual manner on the Earth’s surface. This work considered the relevance of determining g in the didactic laboratory using the pendulum, making a careful analysis of the phenomena that affect the oscillating device, bringing contributions to the teaching of Classical Physics. The first, although modest, is effective, and proposes measuring the oscillation period using two smartphones. The second, a theoretical analysis of the effect of angular amplitude correlated to drag, on the period of pendulum oscillation. The third refers to the validation of two equations that provide the value of g like a function of latitude and altitude, with gravimetric data available on the IBGE website. At the Londrina campus of UTFPR, independent tests were carried out, allowing the value g U T F P R − L d = ( 9.7873 ± 0.0012 ) m ⋅ s − 2 to be obtained. To validate the methodology and verify its accuracy, the two equations that provide g as a function of altitude and latitude were compared with gravimetric data to define which would be most suitable for generating the reference value. This done, it was found that the experimentally obtained value differed by 0.001 m ⋅ s − 2 (0.01%).

A Gravimetria contemporânea vale-se de gravímetros para encontrar o módulo da aceleração gravitacional (g) de forma pontual na superfície terrestre. Esse trabalho considerou a pertinência da determinação de g no laboratório didático por intermédio do pêndulo, fazendo atenciosa análise dos fenômenos que afetam o dispositivo em oscilação, trazendo contribuições para o ensino da Física Clássica. A primeira, embora modesta, é eficaz, e propõe medir o período de oscilação empregando dois smartphones. A segunda, uma análise teórica acerca do efeito da amplitude angular correlacionada ao arrasto, sobre o período de oscilação do pêndulo. A terceira, refere-se à validação de duas equações que fornecem o valor de g em função da latitude e da altitude, com os dados gravimétricos disponíveis no site do IBGE. No campus Londrina da UTFPR, realizaram-se ensaios independentes, permitindo que se obtivesse o valor g U T F P R − L d = ( 9,7873 ± 0,0012 ) m ⋅ s − 2. Para a validação da metodologia e verificação da acuracidade, as duas equações que fornecem g em função da altitude e da latitude foram confrontadas com dados gravimétricos para definir qual seria mais adequada para gerar o valor de referência. Assim feito, verificou-se que o valor obtido experimentalmente divergia em 0,001 m ⋅ s − 2 (0,01%).

Desde o final do século XIX, e posteriormente impulsionado pelo desenvolvimento aeroespacial, a modelagem das vibrações em estruturas metálicas tem demandado grande empenho por parte dos pesquisadores. Acrescentese a isto a importância de se prever os abalos sísmicos e de se minimizar os danos que geram, e se tem mais um significativo propósito pelo estudo das ondas em estruturas. No curso de Física Clássica, aborda-se a ondulatória na perspectiva do oscilador harmônico, das ondas em cordas e em tubos sonoros, analisando-se as ondas longitudinais e transversais. Entretanto, ondas de superfície e ondas extensionais raramente são citadas, de forma que o presente trabalho pretende contribuir na pavimentação desta pequena lacuna, propondo uma atividade prática para calcular o módulo da velocidade das ondas extensionais em hastes de aço e alumínio, empregando as frequências dos harmônicos das ondas estacionárias extensionais. O desenvolvimento teórico é plenamente compreensível ao estudante que possua conhecimento básico de Física e de Cálculo Diferencial e Integral. O aparato experimental é de baixo custo e plenamente disponível. Determinam-se as frequências ressonantes com um telefone celular onde se instalou aplicativo Spectroid, gratuito. Obtiveram-se para as velocidades extensionais vext−Al = (5, 05±0, 02).103m/s e vext-aço = (5, 21±0, 08).103m/s, implicando que os respectivos desvios relativos em relação à literatura foram 1% e 0,6%, muito bons para um laboratório didático. A atividade ainda favorece o aprofundamento dos conceitos relacionados às oscilações e ainda traz fortes elementos lúdicos, como o emprego do telefone celular e o timbre agradável das hastes ressonantes, de forma que sua aplicação é plenamente factível e recomendável.

Since the end of the 19th century, and later driven by aerospace development, the modeling of vibrations in metallic structures has demanded significant effort on the part of researchers. Add to this the importance of predicting earthquakes and minimizing the damage they generate, and there is one more significant purpose for the study of waves in structures. In the Classical Physics course, waves are approached from the perspective of the harmonic oscillator, waves in strings and sound tubes, analyzing longitudinal and transverse waves. However, surface waves and extensional waves are rarely mentioned, so the present work intends to contribute to the paving of this small gap, proposing a practical activity to calculate the modulus of the speed of extensional waves in steel and aluminum rods, using the frequencies of the harmonics of extensional standing waves. The theoretical development is fully understandable to the student who has basic knowledge of Physics and Differential and Integral Calculus. The experimental apparatus is low cost and fully available. The resonant frequencies are determined with a cell phone where the free Spectroid application has been installed. For extensional speeds, were obtained vext−Al = (5.05±0.02).103m/s and vext−steel = (5.21±0.08).103m/s, implying that the respective relative deviations from the literature were 1% and 0.6%, very good for a teaching laboratory. The activity also favors the deepening of the concepts related to oscillations and brings strong playful elements, such as the use of the cell phone and the pleasant timbre of the resonant rods, so that its application is fully feasible and recommendable.

No presente trabalho, apresenta-se uma proposta de atividade didática para estudantes de graduação dos cursos de Física e de Engenharia, visando a determinação do módulo de elasticidade do aço e do alumínio, empregando-se hastes constituídas por estes metais e um smartphone para se obterem os valores das frequências ressonantes dos harmônicos que se nelas estabelecem. A fundamentação teórica considerou a oscilação destas hastes submetidas a flexões simples, com extremos livres. Resolveu-se a equação da dinâmica do movimento para se obter as localizações dos nós, as frequências dos harmônicos, e a relação com o módulo de Young. Os ensaios práticos empregam técnicas de medida bastante simples, equipamentos altamente disponíveis e de muito baixo custo. Os resultados demonstraram a viabilidade da proposta que, além de explorar o ensino por meio de representações múltiplas, possui um forte apelo lúdico e sensorial, inclusive para estudantes com deficiência auditiva. Também há um viés de aplicabilidade para o ensino médio.

In the present work, a didactic activity proposal is presented for undergraduate students of Physics and Engineering courses, aiming at determining the elasticity module of steel and aluminum, using rods constituted by these metals and a smartphone to obtain the values of the resonant frequencies of the harmonics that are established in them. The theoretical foundation considered the oscillation of these rods submitted to simple flexions, with free ends. The motion dynamics equation was solved to obtain the locations of the nodes, the frequencies of the harmonics, and the relationship with the Young’s modulus. The practical tests employ simple measurement techniques, highly available equipment and very low cost. The results demonstrate the feasibility of the proposal, which, in addition to exploring teaching through multiple representations, has a strong playful and sensory appeal, including for students with hearing disabilities. There is also an applicability bias for high school.

ABSTRACT Electrochromic material is a thin film technology that has a close relationship with environmental sustainability since they can control the light and heat that enter and leave a building. Vanadium oxide films are electrochemically active for lithium and electron co-intercalation, presenting low optical variation in the low energy visible light, which is suitable for application as a passive electrode in the electrochromic devices. The spectral double coloration of vanadium oxide thin film has been investigated but the monochromatic, in particular, for high photons energy, remains poorly explored. To understand the optical behavior of the vanadium oxide films, in high photons energy (E > 2.0 eV), films were opto-electrochemically investigated. The films were electron beam deposited and modified by heat treatment in an inert atmosphere. All samples show crystallographic orientation in a [110] direction, and the charge capacity showed to be dependent on the film conditioning. The charge capacity of the as-grown film is about 6 mC while for the film heat-treated at 100 ºC it is five times higher. The vanadium oxide films showed reversible Li+ intercalation, presenting a double spectral and monochromatic coloration. It was concluded that for low energy photons the small polaron model fully explains the phenomenon of double monochromatic coloration, and, for high-energy, the monochromatic double coloration is due to the crystallographic phase transition.

The V2O5 thin films has been widely studied because it has application as ionic host in electrochromic and lithium-ion batteries, two technologies that have an intimate connection with sustainability as substitutes for fossil energies and as agents for improving energy efficiency. In electrochromic technology, V2O5 is applied as a passive electrode due to its high transmittance and small contrast, and its reversibility on electrochemical reactions. To contribute to increase the optical and charge efficiency of V2O5 thin film passive electrodes, were investigated in this work the influence of the morphological properties, crystallite size and roughness, on the reversible specific charge capacity and the respective optical responses. The films morphological properties were modified by varying their thickness to the nanoscale. The films were deposited by thermal evaporation from powdered V2O5. The crystallite size and surface roughness were measured respectively by XRD and AFM. The results showed that the charge capacity is directly proportional to the surface roughness and inversely proportional to the crystallite size. The film optical contrast and the nominal transmittance shows to be improved according to their morphological properties. In conclusion, the V2O5 opto-electrochemical properties can be improved, increasing the efficiency on the light control processes.