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The applications of digital video image to the investigation of physical phenomena have increased enormously in recent years. The advances in computer technology and image recognition techniques allow the analysis of more complex problems. In this work we study the movement of a damped coupled oscillation system. The motion is considered as a linear combination of the two normal modes, i.e., the symmetric and antisymmetric modes. The image of the experiment is recorded with a video camera and analyzed by means of software developed in our laboratory. The results show a very good agreement with the theory.

Multimedia technologies and video analysis allow the design of low-cost physical measurement and data acquisition systems. The number of pixels in the images limits their spatial resolution, whereas their time resolution depends on the number of frames recorded per second. Both characteristics are determined by the video recording system used. We have developed a laboratory system with these characteristics where important improvements have been reached by using image recognition to automate video analysis. In the present work we first examine several image recognition techniques and evaluate them from the point of view of their application to measurement systems. Then we describe the proposed system and the methodology followed in the measurement process. An image of an experimental object is recorded and used as a filter, while the sequence of images of that object in motion become the input frames for the recognition process. Finally, we discuss the results obtained by this measurement process and compare them with those obtained by using traditional measurement techniques.

In our experience of teaching physics for engineering at university level we have learned that the mathematical relationships between the parameters that control a process are important, but not sufficient, to understand a process. Such knowledge will only be consolidated if the new concept is incorporated by student in his field of study. Simulation programs, especially through visualization, can help to attain this target. We have developed three programs using Visual Basic. One of them is devoted to fitting experimental data and is complementary to experimental work; the others focus on dynamics, translation, and rotational movement, helping to understand the Newton's laws. ß

Magnetic braking is a long-established application of Lenz's law. A rigorous analysis of the laws governing this problem involves solving Maxwell's equations in a time-dependent situation. Approximate models have been developed to describe different experiences related to this phenomenon. In this paper we present a new method for the analysis of the magnetic braking using a magnet fixed to the glider of an air track. The forces acting on the glider, a result of the eddy currents, can be easily observed and measured. As a consequence of the air track inclination, the glider accelerates at the beginning, although it asymptotically tends towards a uniform rectilinear movement characterized by a terminal speed. This speed depends on the interaction between the magnetic field and the conductivity properties of the air track. Compared with previous related approaches, in our experimental setup the magnet fixed to the glider produces a magnetic braking force which acts continuously, rather than over a short period of time.The experimental results satisfactorily concur with the theoretical models adapted to this configuration. *