experiments in rigid body mechanics using a remote ...

EXPERIMENTS IN RIGID BODY MECHANICS USING A REMOTE LABORATORY H. Kofman1, R. Pérez Sottile2, S. Concari1,2, A. Sarges Guerra2 1

Facultad de Ingeniería Química. Universidad Nacional del Litoral (ARGENTINA) Facultad Regional Rosario - Universidad Tecnológica Nacional (ARGENTINA) [email protected], [email protected], [email protected], [email protected]

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Abstract Remote laboratories are one of the most advanced ways to implement new computer technology in education. Real experiments are mounted in the laboratory of a certain university, and the access can be done via the Internet. The link is remotely done through the Web, in some cases it is even possible to observe the development of the experiment through a TV camera also connected to the Internet. This allows students to be placed in the actual laboratory. Undoubtedly, these systems represent a huge advantage in science teaching since many laboratories do not have enough equipment to make certain experiments. Once the technological problem of developing the experiment and designing the remote access to it is over, the main questions that arise are didactic in nature: How to approach the implementation of these devices in the teaching environment? How to do instructional design? How to evaluate the results in learning physics? In this paper, we present a general description of the architecture of the devices as well as some didactic strategies for their use in experiments in rigid body mechanics. We also show the results of the implementation of one of the developed strategies with a group of engineering students. They show a meaningful learning of physics concepts and laws related with dynamics and energy of a rigid body rolling down on an inclined plane. Keywords: Remote laboratory, experiment, mechanics, energy, rigid body, physics education.

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NEW TECHNOLOGIES IN HIGH EDUCATION

Laboratory at the University is one of the places where the new technologies have been located to improve experimental practices. The laboratory is defined as a place provided with the necessary means to carry out investigations, experiments and scientific works and also to like experiment or elaborate something [1]. At a time when the number of university students is growing, more sophisticated laboratories and equipment are needed. Apart from real laboratories, virtual and remote ones have been developed through the last decades and are being used in engineering education. [2]. The remote laboratory is one of the most advanced ways to implement new computer technology in education. Real experiments are mounted in a laboratory at a university, and the access can be done via the Internet. The link is remotely done through the Web, it is even possible to observe the experiment through a TV camera also connected to the Internet. This allows students to be placed in the actual laboratory. Undoubtedly, these systems represent a huge advantage in science teaching since real laboratories do not have enough equipment to make different experiments. We present a general description of the architecture of the devices as well as some didactic strategies for their use in experiments in rigid body mechanics. We also show the results of the implementation of one of the developed strategies with a group of engineering students. They show a meaningful learning of physics concepts and laws related with dynamics and energy of a rigid body rolling down on an inclined plane.

Proceedings of INTED2011 Conference. 7-9 March 2011, Valencia, Spain.

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ISBN:978-84-614-7423-3

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Remote laboratories

The “remote laboratory” or “real laboratory with remote access” is made up by a series of devices, materials and instruments organised in a certain place to allow the execution of experiments directed by a distant operator through a communication system, in this case the Internet. Thus, it is different from the virtual laboratory which consists of computer simulations of physical systems. Remotely controlled laboratories are real experiments that can be controlled by users from their computers via the Internet [3]. From a technical point of view, the remote experiment is linked to automatic control and to robotics. Its first applications were directed to solve problems of lack of safety or non habitable conditions of some rooms where certain actions or trials had to be executed [4]. In Fig. 1 it is possible to see the technical drawing of a remote experiment where the experimental device is connected to the PC (the Internet server) through an interface of data acquisition (I/O Card). It is also possible to see how the different users that are connected have access to the remote experiment. Since the experiment made by the different users cannot be kept in folders, a software, capable of administering the access petitions in order and through the permits previously granted, is designed. .

I/O CARD

SERVER

INTERNET

CLIENT E

CLIENT E

CLIENT E

CLIENT E

Figure 1: Experiment in a remote laboratory

The student is not in direct contact with the physical system, but works with it at distance through the Internet either from his laptop at home or from a PC in a computer laboratory in any educational institution. Today, the remote laboratories find in the investigation and the teaching in different engineering areas, an application that grows while they are developed in Europe, Latin America and the USA. In Spain there are remote laboratories at Polytechnic University of Valencia, Spanish University for Distance Education (UNED), Universities of León, Deusto, Valladolid, among others. So as to reduce costs and provide a service to teachers and students, the use of the remote laboratory is generally shared by various institutions. At present, as stated by Gröber et al [5]: “A reasonable use of sensibly chosen

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real experiments as remote labs allows a new form of homework and exercises, as well as project work and the execution of experiments, which usually would be a teacher's prerogative only”. Within the frame of a university education of quality and having solved the problem of connectivity and technical issues, we are working in the didactic designs and their evaluations. 1.1.1 Remote lab for Physics teaching Various universities have developed remote labs with educational aims. For Physics teaching we can mention, among others, the Remote Laboratory of the Physics Department of the Condensed Matter, Crystallography and Mineralogy of the High Technical School of Industrial Engineers of the University of Valladolid [6], where experiments of luminous interference and physical pendulum are offered; the remote laboratories of the University of Murcia [7] that provides experiments with electric circuits and electronics and the Hook´s law experiment at the FisL@bs portal of Spanish universities [8]; the Remote Laboratory at the University of Technology of Sydney housing five sets of different experiments which include tests of coefficients of friction, gravity, static and kinetic friction [9]; the Hands-On Universe, EUROPE (Eu-Hou) Project, a collaboration of hundreds of teachers and scientists from 14 countries, with remotely controlled Physics experiments in mechanics, electromagnetism, optics and modern Physics [10], developed principally at the Remotely Controlled Laboratory Portal of the Technical University in Kaiserslautern (Germany) [3], Tomas Bata Technical University in Zlin and University of Trnava in Czech Republic [11], together with the Laboratory of Magnetism at the Institute of Experimental Physics, of the University of Bialystok (Poland) [12]. In Latin America, there are already remote experiments in movement mechanics at the National University of Colombia [13] and several Physics experiments at universities of Brasil [14]. In Argentina, there are two laboratories that have experiences in Physics to be performed through the Internet: the Remote Laboratory of the Distance Learning Department of Exact Sciences, Engineering and Surveying Faculty of the National University of Rosario [15, 16] where experiences in Electronic Physics are offered; and the Remote Laboratory of the Galileo Group of the Department of Physics in the Faculty of Chemical Engineering of the National University of Litoral.[17]. In the latter there are experiences of electronic circuits as well as a flywheel on an inclined plane, which is going to be the object of analysis of this work.

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METHODOLOGY A mechanics experiment: movement of a flywheel on an inclined plane

A common experiment in the teaching of mechanics in courses of physics at university is the movement of roto-translation of a flywheel on an inclined plane. A flywheel is a mechanical device with a significant moment of inertia used as a storage device for rotational energy. In the traditional practice the experiment consists of letting the flywheel roll on the inclined plane, measuring the time it lasts in running along it. Once the time data and distance covered are collected, the acceleration (considered constant) is calculated. Fig. 2 shows the flywheel used in the remote experiments.

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12,2 mm

16,2 mm 150,6 mm

106,6 mm

Figure 2: Flywheel shape and dimensions

The system has a couple of parallel rails pivoted in a point near the centre. One extreme of the rails is supported by a worm gear, which triggered step by step, moves the extreme vertically to choose the angle of inclination. The system is connected to an acquisition board that digitizes position data and time obtained through a series of photogates. One characteristic of the platform is that it makes it possible to see the experience live through an IP camera. This camera provides photos like the one in Fig. 3.

Figure 3: Image of the experiment observed in real time through a video camera

While the flywheel rolls and moves along the rails the position values regarding time and their representation as points in a graph start appearing. In Fig 4 it is observed a screen capture of the users´ interfaces by which the user introduces the parameters of the experiment (angle of inclination), and receives the data graphically and numerically. Besides, an adjustment by least squares of the data is automatically done to obtain the acceleration, a result that appears on the graph. Clicking on the original, it is possible to see the adjustment graph. Both these graphs can be stored in jpg format while the data can be exported to be later processed with a mathematical software. This way, varied information of the flywheel movement can be obtained.

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If more than one experience is carried out, it is possible to “surf” or see them simultaneously.

Figure 4: User´s operation window

The software used to access remotely the device is in applet Java format, so it is possible to enter through a web page. To be able to run the software, it is necessary to install in the computer a plug-in: JRE (Java Runtime Environment). To use the software, a user´s name and a password are needed and should be requested to the Galileo Group

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Didactic strategies for remote experiments

Once the technological problem of developing the experiment and designing the remote access to it is over, the main questions that arise are didactic in nature: How to approach the implementation of these devices in the teaching environment? How to do instructional design? How to evaluate the results in learning physics? In order to work out new didactic strategies, we have developed a practical work so that the students strictly follow certain learning objectives. To achieve them, the students have to perform some activities that combine theoretical development with experimental work. They should have enough group autonomy to develop their own initiatives, to interact with each other and to ask their teacher only if necessary. In Fig. 5 a summary of the didactic guide used, designed by the teaching team, has been included. The 20 students that participated in the experience are Engineering students, part of the first year course of Physics at the National University of Technology of Rosario. They regularly attend the course at the Regional Faculty of Rosario, a city located at 170 km from Santa Fe, the city where the Remote Laboratory is assembled. Uniformly Accelerated Rectilinear Motion and Roto-Translation Dynamics Objectives: To theoretically deduce the expression of the linear acceleration of the flywheel motion and calculate its moment of inertia. Then, make experiments with different inclinations and compare the experimental results with those that can be predicted from theory. For one of the experiences, calculate the final kinetic energy of the flywheel (translation and rotation), and compare it with the initial potential energy. Activities: 1) Deduce the expression of the acceleration of the flywheel center of mass, assuming a rototranslation motion with no sliding. Check whether it corresponds with the equation (1), where I0 is the moment of inertia of the flywheel and r its axis radius.

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(1) 2) Calculate the moment of inertia of the flywheel, whose data (mass and measures) can be obtained 4 2 clicking on “Flywheel Data”. Check if it gets a value approximate to 1.45 x 10 g cm 3) Carry out experiences with different angles and compare the experimental acceleration with that calculated from (1). 4) For one of the experiments performed, calculate the variation of potential energy between the start and the end of the movement (bear in mind that the total length of the distance covered is 128 cm), and the total kinetic energy of the flywheel at the end of the motion. Draw a comparison. 5) Analyze the experiences carried out and the degree of coincidences among experimental results and theoretical predictions as well as possible sources of error. Figure 5: Didactic guide for remote experiments with the flywheel

Following the rubrics given to the students, it is interesting to analyze to what extend the experimental points can be adjusted to the second grade polynomial function to get the value of acceleration. Then, the students can compare the results with the one calculated through the corresponding PhysicoMathematical model, and deduce scopes and limitations of both procedures. The most relevant physical concepts involved in the subject are: moment of inertia, energy, mechanical work, and acceleration. Besides from the experimental activities, pen and paper problems were solved in class. Finally, conceptual meaningful learning as well as collaborative work promoted in students by experimenting with the remote lab were evaluated. Learning of Physics concepts related to the movement of a solid rigid body was evaluated by solving a problem of a flywheel rolling up on an inclined plane (Fig. 6). Problem The flywheel shown in the figure has m1 = 10 Kg, m2 = 2 Kg and a radius R1 = 10 cm and R2= 4 cm. It o rolls up an inclined plane (10 ) with no sliding a) Make a free-body diagram of the flywheel and identify both the conservative and non conservative forces. b) Express the relationship between the work of the forces that operate on the flywheel and its kinetic energy, explaining the meaning of each symbol and term in the equation. c) Calculate the minimum length of the plane up to which it could climb if at its base, the center of mass has a speed of 1.00 m/s. Obs.:

Suppose that it does not slide at any time and rolls no sliding from the onset. m1 


m2 


m1 


R1
 R2 


Figure 6: Problem used for evaluating conceptual and attitudinal learning

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RESULTS

The main results of the execution of the remote experiment of the flywheel on the inclined plane may be formulated as follows: 1. The remote experiment was developed and successfully implemented on a first course of Physics with Engineering students.

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2. The technical and didactic requirements to use such experiment were easily fulfilled. It was possible to visualize in actual time and with excellent resolution the experiences performed. 3. The students were able to perform the experiment, gather and process data, and to calculate the moment of inertia of the flywheel and its acceleration as well as its mechanical energy. 4. The learning promoted by the execution of experience was highly significant since the students were able to solve in the exam the new problem they were presented with. 5. The main difficulties in the execution of the experience were related to the previous necessary port triggering when the connection was made from computers with restricted access. 6. The remote use of the experiment allowed the execution of adjustments in the software and in the different elements that triggered the experience. The execution of experiments by a remote means integrated to the resolution of pen and paper problems and other learning activities are a potential means to promote a meaningful learning of concepts and laws of Physics among Engineering students. Finally, the use of remote experiments requires a collaborative work among teachers of different universities through a network of investigation and teaching; in this case, the National University of Litoral and the National University of Technology.

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[9]

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[10] The EU-HOU Project. Access 10/01/11: http://www.euhou.net/index.php?option=com_content&task=view&id=187&Itemid=13 [11] M. Ožvoldová, F. Schauer and M. Beňo REMOTE FREE FALL EXPERIMENT FOR DYNAMIC STUDIES 3rd International Symposium for Engineering Education, 2010, University College Cork, Ireland. Access 11/01/11: www.ucc.ie/ucc/depts/foodeng/isee2010/pdfs/.../Ožvoldová%20et%20al.pdf

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[12] Maziewski, A; Dobrogowski, W and V Zablotskii, V. GloLab: creating a global Internet-accessible laboratory. Physics Education, 2007. Volume 42, Number 1, 72 [13] Barco, H; Arango, P; Restrepo E. Laboratorios Remotos de Física General. Una Alternativa Para la Enseñanza. http://www.istec.org/wp-content/gallery/ebooks/ace/docs/ace-seminar09-final8.pdf [14] Juarez Bento da Silva. Utilização de experimentação remota como suporte a ambientes de ensino-aprendisagem na rede publica de ensino. FRIDA 2009. Access 12/12/10: http://www.programafrida.net/docs/frida2009/presentaciones/Juarez_Bento_da_Silva.pdf [15] Laboratorio Remoto del Departamento de Educación a Distancia. Facultad de Ciencias Exactas, Ingeniería y Agrimensura. Universidad Nacional de Rosario. Access 15/01/11: http://posgrado.fceia.unr.edu.ar/?mod=cargarContenido&contenidoid=17 [16] Marchisio, S; Lerro, F and Von Pamel, O. Use of a remote laboratory to promote meaningful learning in the teaching of electronic devices. Pixel-Bit. Revista de Medios y Educación. Nº 38 Julio- Diciembre 2010 pp. 129 – 139 http://www.sav.us.es/pixelbit/actual/10.pdf [17] Laboratorio Remoto del Departamento de Física. Facultad de Ingeniería Química. Universidad Nacional del Litoral. Access 15/01/11: http://www.fiqus.unl.edu.ar/galileo/

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