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Um importante fenômeno físico, com várias aplicações tecnológicas,é o conhecido efeito Doppler. Face a sua importância, esseé um tema comum em praticamente todos os livros de ensino médio e superior. Não obstante,é um tema de difícil abordagem experimental, principalmente em escolas que não possuem um laboratório didático bem equipado. Neste trabalho, apresentamos um experimento didático, que permita a medida da frequência Doppler para ondas sonoras. Para tal, utilizamos como recursos didáticos aparelhos que fazem parte do cotidiano dos alunos, a saber, tablets, smartphones e softwares livres. Acreditamos que a utilização destes aparelhos torna a proposta de "baixo custo"e acessível a grande parte das escolas brasileiras. Palavras-chave: Efeito Doppler, experimento de baixo custo, tablets e smartphones.An important physical phenomena, with many technology applications, is the Doppler effect. In view of its importance, this is a common subject in high school or college books. However, it is a subject of difficult experimental approach, mainly in schools that do not have a well equipped teaching laboratory. In this paper, we present a didactic experimental, that enable the measure of Doppler effect for sound waves. We use as didactic resources devices that are part of daily life of students, namely, tablets and smartphones. We believe that the use of these devices makes this a "low cost" proposal and accessible of the most Brazilians schools. Keywords: Doppler effect, low cost experiment, tablets and smartphones. IntroduçãoNosúltimos anos o ensino de física vem enfrentando um de seus maiores desafios: sua prática para uma geração de estudantes imersos na tecnologia e na facilidade de acessoà informação. A sala de aula atual na disciplina de física em qualquer segmento de ensino pode ser considerada a materialização do desafio citado. Neste sentido, abordagens que envolvam tecnologias de informação e comunicação (TIC's) tem grandes chances de despertar o interesse e, sobretudo, facilitar o diálogo entre professores e alunos [1,2]. Atualmente, muitos trabalhos têm explorado novas tecnologias para auxiliarà aprendizagem no ensino de física, podemos citar, trabalhos de modelagem computacional [3][4][5], simulação * Endereço de correspondência: wagner.balthazar@ifrj.edu.br.e experimentos virtuais [6][7][8][9], softwares [10-12] e vídeo-análise [13,14]. O uso de smartphones e tablets como instrumentos de medidas associadosà experimentação também tem sido investigados [15][16][17][18]. Esses recursos didáticos, quando utilizados em sala de aula, podem contribuir para enriquecer a abordagem didática e o processo ensino-aprendizagem.Os Parâmetros Curriculares Nacionais do Ensino Médio [19] trazem diretrizes para o ensino das ciências que valorizam a compreensão da natureza e as tecnologias, visando a inserção do educando na sociedade de forma a promover um exercício crítico da cidadania. Assim, temas que envolvem aplicações tecnológicas importantes são mais potencialmente significativos para os alunos. O efeito Doppler (ED...

The installation procedure of a torpedo anchor is the release of the torpedo from a high enough position from the sea bottom to allow the device to reach the terminal velocity. A sufficient kinetic energy at the bottom is essential for the penetration. Besides this, the anchor has to reach the bottom in an upright position to maximize the final holding power in all directions. The present work addresses two hydrodynamic aspects for the installation design and analysis. The first is the drag evaluation and the second is the directional stability. If the drag is to be kept small, then the terminal velocity should be high. The work shows that parameters like the mass and the shape are essential for this. On the other hand, the shape and mass distribution have a strong influence on the directional stability. One important parameter is the rear line length connected to the anchor. This line is necessary for further connection with the final mooring line and influences both the terminal velocity and the directional stability. The work addresses all these aspects under the light of an innovative model test setup to be performed in a deep ocean basin. This kind of model testing has been conceived specifically to attend the torpedo anchor evaluation.

a b s t r a c tThis study proposes an innovative turbine that consists of a vertical flat plate, which is allowed to rotate freely about a vertical axis of symmetry and exploits the autorotation phenomenon to harvest the energy from the current. This system is called here Vertical Axis Autorotation Current Turbine (VAACT). The VAACT utilizes the extra mass moment of inertia to improve the rotational quality which is state of the art in this turbine. This paper covers the principle behind the VAACT and outlines procedures and results for experiments proving the basic feasibility. Also, the operation of the turbine will be discussed by experimental results of the torque coefficient, performance and kinematic parameters. Tests were conducted in LOC (Laboratory of Wave and Current) at COPPE/Federal University of Rio de Janeiro (COPPE/ UFRJ).Utilizing the extra mass moment of inertia on the VAACT causes to extract the energy as an efficient turbine in very low head current. The maximum VAACT efficiency has been obtained experimentally in optimum non-dimensional moment of inertia in range of 0.5 and 0.6.

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This study examines the efficiency of a vertical axis current turbine (VACT) according to various non-dimensional mass moments of inertia. The vertical axis current turbine of drag force type with flat plate-shaped blade is tested. From experiments in a circulating water channel the angular velocity, the power coefficient and tip speed ratio of the vertical axis current turbine are obtained. The property changes for various conditions give the relationships between efficiency-related parameters. The maximum power coefficients of experiments occur at the tip speed ratio of approximately 0.35∼0.40. From the experiments, turbine is found to give a 7% power coefficient which related to I* = 0.52.

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