The purpose of this study was to explore the effectiveness of the conventional high school instruction about conservation of mechanical energy in Canton Sarajevo. To that end we tested 441 high school students from six different schools in Sarajevo (Bosnia and Herzegovina) for their competence to apply the law of conservation of mechanical energy. Concretely, students were expected to solve 5 open-ended tasks that covered conceptually different situations. In each task we asked a set of sub-questions to check whether the students possess all the prerequisite sub-competencies for systematic reasoning about conservation of mechanical energy. In addition, we investigated how students’ ideas about conservation of mechanical energy were affected by the choice of the physical system, as well as by the choice of the observed time interval. Data analysis was performed on the level of individual tasks. The students’ written answers were analyzed and the frequencies of most prominent student responses were reported. Generally, it has been shown that most high school students from Sarajevo fail to identify and distinguish internal, external, conservative and non-conservative forces. Also, many students think that applicability of the conservation law does not depend on the chosen physical system and its evolution over time. We could conclude that high school students’ use of the conservation law is mostly based on remembering similar problem solving experiences, rather than on relevant strategic knowledge.

Single slit diffraction is part of many high-school physics curricula throughout the world. In this study, we aimed to investigate whether high-school physics teachers from Bosnia and Herzegovina, Serbia and North Macedonia are adequately prepared to discuss with their students about various aspects of the single slit diffraction pattern, particularly about vertical length of diffraction fringes. To that end we conducted a written survey which included 57 high-school physics teachers. Besides asking teachers about students’ difficulties in learning about single slit diffraction, we also asked them to specify their own difficulties with this topic and required them to solve a conceptual task. Almost every second teacher believed that vertical length of diffraction fringes can be increased by changing shape or width of the slit and only 1 out of 57 teachers managed to correctly answer why diffraction fringes become shorter when we move away from the central maximum. We concluded that physics teacher education programmes should be changed to develop understanding of both, horizontal and vertical aspects of the diffraction pattern. To that end it is useful to provide learning opportunities which encourage combining ray and wave model of light.

Physics curricula around the world recognise energy as one of the core concepts in science (Duit, 2014), as it is fundamental in development of integrated scientific understanding of phenomena (Linn et al., 2006; National Research Council, 2012; Nordine et al., 2011). Importance of the energy concept is also recognised by PISA and TIMSS studies and is reflected in many science standards (National Research Council, 2012; Next Generation Science Standards, 2013). However, research about students’ energy conceptions keeps showing that students at all educational levels have significant difficulties with the concept of energy (Goldring & Osborne, 1994; Lawson & McDermott, 1987; Neumann et al., 2013; Pride et al., 1998). Concretely, students exhibit difficulties with understanding work-energy processes (Van Huis & Van den Berg, 1993), energy degradation and energy conservation (Goldring & Osborne, 1994; Liu & McKeough, 2005; Neumann et al., 2013). Thereby, a large number of studies detected conservation of energy as the most difficult aspect of the energy concept (Lindsey et al., 2012; Neumann et al., 2013; Van Heuvelen & Zou, 2001; Van Huis & Van den Berg, 1993). In fact, only a very few students develop deeper understanding of energy conservation until the time they finish secondary school (Herrmann-Abell & DeBoer, 2018). For purposes of improving the quality of teaching about energy, it is useful to identify possible sources of above-mentioned students’ difficulties. Firstly, it is important to note that many students’ difficulties with the energy concept may be related to students’ (mis)understanding of systems (Seeley et al., 2019; Van Heuvelen & Zou, 2001; Van Huis & Van den Berg, 1993). Consequently, students should be helped to recognize the importance of carefully choosing the physical system, if one wants them to gain a functional understanding of energy conservation (Lindsey et al., 2012; Seeley et al., 2019). Such system-based Abstract. Conventional teaching about the law of conservation of mechanical energy (LCME) often results with students trying to solve problems by remembering similar problems they already covered in classes. Consequently, many students fail to transfer their knowledge to simplest real-life problems. Therefore, a pre-test – post-test quasi-experiment was conducted to evaluate the effects of an alternative, system-based approach to teaching about LCME. The study included 70 upper-secondary students from the First Bosniak Gymnasium Sarajevo, Bosnia and Herzegovina. Firstly, all students learned about energy in a conventional way. Then they wrote a test on LCME and had three additional hours of teaching about this topic, where one group of students learned in line with the forces-variant of the system approach (e.g., discussing conservative and nonconservative forces) and the other group with the process-variant of the same approach (e.g., discussing system’s states and processes like in thermodynamics). For both variants, only three hours of system-based teaching proved to substantially improve the students’ level of LCME understanding compared to the level of understanding they had after conventional teaching. It follows that the system approach may work well at the upper-secondary level, if it is introduced through the scaffolding-andfading technique.

Teaching the concepts of electrical and thermal transport in solids begins in elementary school through simple macroscopic models and progressively develops to microscopic quantum models within specialized university courses. Educational research has pointed to a number of misconceptions in this field, especially when it comes to understanding related phenomena at the microscopic level. This study aimed to design an appropriate open-ended version of the concept inventory to test the level of students’ understanding of microscopic models of electrical and thermal conduction in solids (METCS). The METCS concept inventory consists of 27 open-ended questions that examine the understanding of different and interrelated concepts. We used it as a tool for conducting interviews on a sample of ten students from the universities of Rijeka and Split (Croatia). The results of our research confirmed some previously discovered students’ misconceptions and revealed a wide range of new ones. These results can be used to stimulate student discussions and to design curricula and lecture plans for more efficient teaching of transport phenomena in solids. The obtained spectrum of misconceptions will serve as a reference tool for the development of a multiple-choice conceptual METCS test to allow research on larger sample.

Maintaining item banks that continually reflect the measured construct can be achieved through periodically removing obsolete items and adding validated items.

In this study we investigated whether combining external visualizations with extreme case reasoning may facilitate developing of conceptual understanding about wave optics. For purposes of answering our research question we conducted a pretest-posttest quasi-experiment which included 179 students from a first year introductory physics course at the University of Zagreb, Croatia. Students who were guided through extreme case reasoning in their wave optics seminars significantly outperformed their peers who received conventional teaching treatment. Findings from our study suggest that combining external visualizations with extreme case reasoning facilitates development of visually rich internal representations which are a good basis for performing mental simulations about wave optics phenomena. In addition, it has been also found that many students use the “ closer to the source implicates greater effect ” p-prim when reasoning about certain relationships, such as the relationship between fringes’ dimension and slits-screen separation.

Successful application of the Huygens–Fresnel principle often requires reasoning about the interplay of aperture and light beam dimensions for purposes of identifying the unobstructed part of the light beam which is the source of secondary waves. Therefore we decided to identify university students’ ideas about the role of this interplay in the formation of diffraction patterns. We conducted a survey research with 191 first-year students from the Faculty of Chemical Engineering and Technology at the University of Zagreb, Croatia. They were administered six constructed-response questions in which aperture or laser beam dimensions were varied and students were expected to verbally and pictorially describe how these changes would affect the diffraction pattern. It has been shown that 63% of students think that a change in the length of the vertical slit necessarily results in a change of the diffraction pattern, even when the illuminated portion of the slit remains the same. In addition, it has been found that nearly 40% of students believe that in optical grating diffraction an increase of beam diameter leads to bigger diffraction fringes. A possible way to overcome some of these difficulties would be to insist on consistent application of the Huygens–Fresnel principle.

A 32-item scale that can be used to measure physics students' understanding of introductory level wave optics.

Animations are widely used in today’s science classrooms. Therefore it is very important to explore under which conditions animations are most effective. In earlier studies it has been generally shown that the effectiveness of instruction largely depends on management of cognitive load. The aim of the present study was to compare the effect of Physlet animations, printed sequences of selected animation frames and traditionally presented static pictures on understanding about lenses and levels of cognitive load. According to the results of a quasi-experiment that included forty nine high-school students, Physlet-based teaching generally leads to higher germane load and consequently to more effective learning than the traditional approach. Particularly high levels of germane load have been found for Physlet-based problems . These findings can be accounted for by the interactivity feature of Physlets.

ABSTRACT Background: It is widely known that for many students it is very difficult to correctly predict how thermal expansion affects the appearance of a metal plate with a circular hole. Interviews with school teachers show that the source of this difficulty could stem from the fact that students’ internal visualizations of an arbitrary object’s thermal expansion often boil down to visualizing changes along one dimension only. Purpose: In this study, we investigated how students’ mental models about one-dimensional expansion can be extended for purposes of running mental simulations about expansion along two dimensions. Sample: To that end a pretest-posttest quasi-experiment has been conducted, with 100 students in the control group and 95 students in the experimental group. Design and methods: Whereas control group students received traditional instruction with a focus on formal representations, in the experimental group the students were led to draw an analogy between heating of a straight rod and a circular rod of same length, whereby the internal structure of the rods was represented by springs. Results: Eventually, it has been found that students from the experimental group were significantly more successful at predicting the effects of thermal expansion, especially within contexts of objects with holes. Conclusion: Analogies and extreme case reasoning can be effectively used for helping the students to correctly transfer their mental models about one-dimensional expansion to situations that require reasoning about expansion along two dimensions.

It is well known that many students have tremendous difficulties with applying Gauss’s law for purposes of solving quantitative as well as qualitative problems. In this study, it was investigated how understanding of Gauss’s law can be facilitated by analyzing the superposition of electric field vectors for increasingly complex geometric configurations of charges. Actually, in the spring semester of academic year 2016/2017, a pretest-posttest quasi-experiment was performed with 180 students from the Faculty of Chemical Engineering and Technology in Zagreb, Croatia. The student sample has been divided into three control subgroups and three experimental subgroups. Control subgroups (Nc=93) received a traditional teaching treatment while in the experimental subgroups (Ne=87) students showed how reasoning about superposition of electric field vectors can be transferred from relatively simple configurations of charges to more complex ones. At the posttest, students from the experimental group proved to be significantly more effective in solving qualitative problems on Gauss’s law. The results from our study support the idea that development of analogical, visually rich models facilitates the meaningful learning.

Abstract Background: Bullying as a stressor in the workplace has been evaluated in numerous settings. It has never been evaluated in the emergency medical service (EMS) environment where bullying can occur from many different sources. The Negative Acts Questionnaire-Revised (NAQ-R) is a 22-question validated tool for evaluating bullying. Our hypothesis was that we could identify a shortened version of the NAQ-R that identifies bullying as accurately as the full screening tool. Methods: This was a cross sectional study of EMS providers in our local EMS transport agency. The local EMS agency transports approximately 50,000 patients per year and is a paramedic level response system. Results on the NAQ-R were on a 5-point Likert scale for each of 22 different categories of bullying that were summed by adding each questions 1–5 response for the 22 questions. Respondents were also categorized as victims or non-victims of bullying based on being positive for any of the 22 types of bullying at least once a week. We performed a binomial decision tree analysis and a cross-validation. Results: Data were collected from 153 providers. Mean age was 33 ± 10 years and 50% were male. Total years in EMS were 8 ± 8 years. NAQ-R summed results in our group ranged between 22 and 88, with an average of 40 ± 15. A NAQ-R score of 33 or less was 91% accurate in identifying non-victims and a score of 45 or more was 94% accurate in identifying victims. The majority at 51% (77/152) of respondents were victims of one or more types of bullying. A combination of five questions was 94% accurate in identifying a victim of bullying among EMS providers. Cross validation resulted in a misclassification risk estimate of 0.12 ± .03. Conclusion: NAQ-R bullying scores in EMS are similar or higher than numbers in other fields. Five questions on the NAQ-R were 94% accurate in identifying victims of bullying in EMS providers.

Earlier research has shown that students have tremendous difficulties with understanding certain aspects of rolling without slipping, such as the zero-velocity at the contact point and plausibility of application of the law of conservation of mechanical energy despite action of the friction force. The aim of this research was to explore whether using analogies and reasoning about extreme cases can facilitate conceptualization of the above-mentioned phenomena. A pre-test – post-test quasi-experiment has been conducted, with 93 students in the control group (CG) and 91 students in the experimental group (EG). Whereas control group students received conventional teaching, in the experimental group rolling of a cylinder has been considered as a special case of a tumbling prism for which the number of prism surfaces tended to infinity. The results of analysis of covariance showed that students from the experimental group significantly outperformed their peers from the control group on the Rolling Motion Concept Test (RMCT). Between-group differences were greater on test items that required higher level of cognitive transfer. This research suggests that using analogies and extreme case reasoning can facilitate comprehension of certain seemingly counterintuitive aspects of rolling motion. Keywords: analogy-based teaching, energy conservation, extreme case reasoning, misconceptions, rolling motion.

Earlier research has found that it is useful to distinguish situations in which students construct external representations on their own from situations in which they are expected to interpret already provided external representations. One type of representations that is particularly important for teaching mechanics is the free-body diagram. In this study, we investigated how inclusion of free-body diagrams into problem statements influences students' performance in solving mechanics problems. To that end two versions of a five-problem assessment instrument that only differed with respect to the inclusion/non-inclusion of free-body diagrams (FBDs) were administered to two groups of first year physics students. It was found that inclusion of free-body diagrams into the problem statements not only did not facilitate problem solving, but also impeded it significantly. Particularly large between group differences, in favor of the group not provided with FBDs, were detected for problems that required use of free-body diagrams showing resolution of forces into components. The results of our study indicate that consistency between internal and external representations of knowledge is a very important requirement for effective problem solving and effective learning of physics, in general. This consistency is most easily established when students use self-constructed external representations.