Teaching Physics through Experimental Projects - Science Direct

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ScienceDirect Procedia IUTAM 20 (2017) 189 – 194

24th International Congress of Theoretical and Applied Mechanics

Teaching Physics through Experimental Projects Catalina Sterna*, Carlos Echeverríaa, David Portaa a

Departamento de Física, Facultad de Ciencias, UNAM, Ciudad Universitaria 04510, Ciudad de México

Abstract

Experiments designed by students at any level is a fun way to learn physics. Laboratory activities can help students acquire, integrate and construct knowledge in a friendly way. For the last 15 years, we have promoted experimental work as projects in theoretical courses. The enthusiasm students have shown, even though they have to spend many extra hours, contrasts their dislike for traditional laboratory courses where they follow recipes. In this paper, we present the original project and its influence in other courses and in new curricula. We will not address the epistemological aspects [1] and give only a slight overview of pedagogical advantages of this approach. © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license © 2016 The Authors. Published by Elsevier B.V. Peer-review under responsibility of organizing committee of the 24th (http://creativecommons.org/licenses/by-nc-nd/4.0/). Congress of Theoretical and committee Applied Mechanics International Peer-review under responsibility of organizing of the 24th International Congress of Theoretical and Applied Mechanics Keywords: Experimental Courses; Teaching Physics, Science Experiments

1. Introduction The physics curriculum at the School of Science of the National University of Mexico has been very theoretically oriented since its creation. Laboratory courses were mostly attached to their theoretical counterpart, and in many cases, the lab reports were not even taken into account for the final grade. To solve the problem, in the last revision of the curriculum, laboratory courses became independent. Unfortunately, they preserved the old equipment with the old methodology, where students receive a set of instructions on how to do a certain experiment, and on the exact procedure required to analyze the data. Most students find these courses boring; they claim that they do not learn anything and many change major to mathematics with the hope of becoming good theoretical physicists. There is a myth that physics majors in our department do not like experiments. For the last fifteen years we have promoted experimental work even in theoretical courses. We have the conviction that the design, development and presentation of these projects by the students, not only helps them to

* Catalina Stern. Tel.: +52-555-622-4802. E-mail address: [email protected]

2210-9838 © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of the 24th International Congress of Theoretical and Applied Mechanics doi:10.1016/j.piutam.2017.03.026

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understand better the specific course, but integrates and organizes knowledge from previous courses, justifies the use of various techniques for data processing and contributes to the improvement of written and spoken language. Most of our experiments are in fluids because that is our area of research. Fluid dynamics appears in the physics curriculum in two compulsory courses, at the sophomore level (3 rd semester) in “Collective Phenomena” and at the senior level (7th semester) in “Continuum Mechanics”. In both, students can choose an experimental, numerical or theoretical final project. Surprisingly, eighty five percent choose an experimental project. In some cases, especially at the senior level, the teams get organized and do the experiment and the simulation. In recent years students from other majors, earth sciences and biomedical physics, are also taking both courses. There are several optional courses in addition that we can teach. Many projects are done in the Hydrodynamics and Turbulence or in the Acoustics Laboratories where other students are doing research, working on their undergraduate or graduate thesis, not related to the courses. There is a strong interaction between all students. They learn from each other, the more advanced students discuss the feasibility of the projects and give suggestions, creating a very friendly atmosphere that most students enjoy. It is important to note that some students choose to continue their work after the course is finished. 2. Basic Ideas and Methodology Students come from high school very often convinced that there is a scientific method. In traditional laboratory courses we reinforce the idea; we expect students to do many things: observe, measure, understand the measurement process, determine the variables and processes that take place, determine the uncertainty of the measurement, calculate error propagation, make hypothesis, make calculations and graphs, find relationships between variables, relate them to previous knowledge, conclude and make proposals for better experiments all in perfect Spanish, and all in three hours. To simplify the process we give them a list of instructions. The set of experiments is the same every semester. Students find the process boring even when the experiments are interesting because we don’t give them enough freedom to think and propose. This is not the way we do research. In the project system students are advised from the beginning of the course that 30 or 40 per cent of their grade will depend on a project that they will have to choose. They have several weeks to decide what they are going to work on. They usually choose to repeat an experiment reported in the literature or continue an existing project in the lab, but sometimes they develop their own ideas. They have to submit a proposal with the names of the participants and a description of how they are going to develop their ideas. Each team consists of three students, but more can participate if they combine experiments with numerical simulations; some students like to work by themselves. The proposals are discussed among teaching assistants and the advanced students in the laboratory to decide its feasibility considering space, equipment and time. This is sometimes very complicated for the teaching team because the approach to each problem is different. Once the projects are accepted and the procedure is discussed with the team, they do the work in one of our laboratories or at home; very often they have to build simple devices. If necessary we ask other colleagues for advice and help, especially in the numerical part. Lasers and high speed cameras are a wonderful tool to visualize the very complex behavior of fluids, but normal video cameras give also excellent results. We have also enough material to obtain schlieren and shadowgraph images. Often we ask other laboratories for equipment and space. Then the most interesting process begins because students are used to blackboard or demonstration experiments that always work. This time they have to things happen, they have to think when they obtain the results different from what they expected. At each step they have a better understanding of the problem and usually modify the procedure. It is a dynamical process with constant interaction between the hypothesis, the experiment, and the results. New personal knowledge is built on previous knowledge and acquired abilities. This process helps students to integrate what they already know, to realize that mechanics is not separated from optics or electricity and magnetism, and that what they know of mathematics is useful. They very often have to use


everything they know from previous physics and math classes to mount an experiment. They learn at every step in a horizontal way, many aspects of the problem at the same time. They understand why it is important to determine the uncertainty of the measurements and the need of data analysis becomes clear. Of course, this intellectual process does not happen only in a laboratory, but it is a friendlier environment where they can confront their ideas with other students. Everybody learns, including the teachers. At the end they have to prepare a fifteen minute presentation. They have to choose the most important aspects of their project, and present it to the classroom. They also have to turn in a term paper that includes everything they proposed, their results, conclusions and a bibliography. The teaching assistants and the professor give the project a grade after analyzing together the procedure of each team. We are convinced that a student that moves independently in the laboratory will acquire enough confidence to look for answers by him or herself. 3. Examples Some of the projects have resulted in an interdisciplinary collaboration. For example the analysis of the escape manoeuver of a Xiphophorus montezumae (Fig. 1a), a small fish with a long rigid tail, helped the PhD thesis of a biology student. The objective of the thesis was to determine whether this tail is mainly ornamental or if it has any use for the survival of the animal. They already knew that fish with longer tails need more oxygen to swim in a straight line. So we designed a tank to observe the escape maneuver when the tank was perturbed. Students in our class measured the angle and speed of escape as a function of the tail size. The final result was that the tail was merely ornamental. Students from different majors propose very different types of projects, and now interdisciplinary teams are being formed. They study vortex dynamics applied to the atmosphere, or turbulence in ducts with different diameters or with non Newtonian fluids. They also project their personal interests. Swimmers have studied the velocity field around themselves during a dolphin kick (Fig.2), the thermal mixing after a water polo match or the cavity created when the start dive is done from different positions. If the projects are very good, students can continue working and present them in the congress of the Division of Fluid Dynamics of the Mexican Physical Society or in the education sector of the National Congress of Physics.

Fig.1 a) Xiphophorus montezumae is a small fish with a rigid tail. b) Experiments showed the influence of the length of the tail in the escape maneuver

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Fig.2 Bottom: swimmer passing through a bubble curtain. Top: velocity and vorticity fields. This student continued her project and recently obtained a master degree in the same subject.

Sometimes the project becomes an undergraduate thesis or a social service. (It is mandatory for all students in Mexico to spend six months doing a social service before they receive their undergraduate degree.) Several congress presentations have been accepted for publication (Fig. 3) [2,3], others have won prizes at the Gallery of Fluid Motion of the Congress mentioned above and some videos have been presented in the Gallery of Fluid Motion of the American Physical Society (Fig 4) [4,5]. We have a web page called “Passion for Fluids” (Pasión por los Fluidos) that we hope to make bilingual soon, and a youtube channel where the projects are displayed. Students are very happy to see their work in the web and help with the design, so we are in constant reconstruction. It is important to note that this procedure implies many hours of additional work because they have to fulfill all the requirements of the theoretical course. 3.1. Influence in new curricula These ideas have permeated to other courses that have a different structure. The senior laboratory courses did not have enough room and equipment in good conditions to receive the required amount of students per semester in good conditions. This situation created a serious problem because many students were unable to finish on time their credits. We were able to convince the department that a set of three projects in research labs during the semester was enough to validate the contemporary physics lab. Many of the teachers are researchers in the Physics Institutes on campus so it has not been complicated for them to receive teams of two students for four weeks to do a short experiment. Students and professors are very happy with this arrangement. Many undergraduate laboratories are working with projects now. In the electronics course, junior level, a team designed a robot that is able to drill a hole in the ground, plant a defined number of tomato seeds and move the required distance to drill a new hole.

Fig. 3 Left: Kaye Effect, Right: wake behind a table tennis ball


Fig. 4 a) Ranque- Hilsch Tube visualized with powder, b) Cavity and jet formed by splashing of a sphere c) Shock wave visualized with Rayleigh Scattering

Finally, the new major of biomedical physics designed the first four experimental courses with variations of the project scheme. A team of two students spends four weeks working on a project and the shift to another project. However, the second team does not start all over again but continues the work of the precedent team and the third team continues what the second team did. This requires communication and discussion among all the students that participate in the same project. At the end of the semester, the team that worked at the end of each project presents everything. The results have been amazing, for example, 3 rd semester students were able to build an oximeter. 4. Conclusions The main conclusion is that students enjoy learning through projects. The number of students that enroll in our courses continues to increase. We do believe that the learning process required in designing and bringing a project to an end provides tools to the students that will be useful in any research and many real life situations. However, the amount of time that we and our graduate students invest is enormous because the school environment is not prepared for this type of teaching.

Acknowledgements We acknowledge support from DGAPA UNAM through project PAPIME PE105716 and from the Department of Physics of the School of Science of the National University. One of us, C. Stern, would like to acknowledge the support of several generations of undergraduate and graduate students that have worked in the Acoustics and the Hydrodynamics and Turbulence Laboratories.

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References [1] Koponen, I.T. & Mäntylä T. Generative Role of Experiments in Physics and in Teaching Physics: A Suggestion for Epistemological Reconstruction, T. Sci Educ 2006; 15: 31 [2] Ramírez de la Torre R.G, Vargas Ortega D.C, Centeno SierraM.S. , Méndez Fragoso R. and Stern Forgach C., Characterization of a Bubble Curtain for PIV Measurements; Selected Topics of Computational and Experimental Fluid Mechanics; Klapp Ruíz-Chavarría, Medina Ovando, López Villa & Sigalotti, Springer Environmental Science and Engineering, 2015, pp-261-270 [3] Ochoa Morales J.E., Ramírez Guerra C. & Stern Forgach C. New Experiments on the Kaye Effect, Experimental and Theoretical Advances in Fluid Dynamics, 2012 pp.433-441, Ed. J. Klapp, A. Cros, O. Velasco, C. Stern y M.A. Rodríguez–Meza, Environmental Science and Engineering, Springer Verlag [4] Porta Zepeda D., Echeverría Arjonilla C., Stern Forgach C & Ley Koo M. Visualization of Flow Inside a Ranque Hilsch Tube. J. Klapp et al. (eds.), Fluid Dynamics in Physics, Engineering and Environmental, Applications, Environmental Science and Engineering, SpringerVerlag Berlin Heidelberg. 2013 pp. 523-525. [5] Gutiérrez Quijada S.V., Salazar Romero M.Y. & Stern Forgach C. Splashing of a Solid Sphere Impinging on Various Fluids. J. Klapp et al. (eds.), Fluid Dynamics in Physics, Engineering and Environmental, Applications, Environmental Science and Engineering, SpringerVerlag Berlin Heidelberg 2013 pp. 527-528.