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Classroom experiments related to investigating the centripetal force are often underrepresented in the physics teaching practice. This is largely due to the fact that schools lack the proper equipment and teachers lack the time to perform the rather tedious data collection procedures which are characteristic for some of the traditional experimental setups. A possible solution to this problem is to develop and utilize alternative experimental setups within the digital environment. In fact, earlier research has shown that new generations of students are highly motivated to learn physics in digital environments and that these environments often provide at least as efficient learning of concepts as traditional environments. In this article, we present an augmented reality Android application named CEntripetalForceAR (CEFAR) that allows students to experimentally investigate how centripetal force depends on the period of orbital motion and the orbital radius. A possible pedagogical approach to using CEFAR is also described, including suggestions on how CEFAR can be used to overcome some of the most common misconceptions related to circular motion. A user experience survey which included 163 first-year university students showed that CEFAR can be awarded an excellent usability rating. Most students stated that the application helped them to improve their understanding about centripetal force either by visualization or by the possibility to explore cause and effect relationships.

Coulomb’s law is a typical representative of the inverse-square laws that appear in various learning contexts in physics. In the usual classroom setting, most students do not have the opportunity to experimentally discover the interdependence of variables described by this law. Recently, digital technologies have become more prevalent at all levels of education. Teachers and researchers are successfully using computer-based simulations to improve physics education. Augmented reality is one of the emerging digital technologies that have the potential to improve students’ understanding of a wide range of educational topics. Nevertheless, it is advisable that students and teachers are familiar with the most efficient use of selected digital tools before using augmented reality-enriched physics lectures. In this paper, we present our augmented reality simulation called CoulombsLawAR, which could be useful for teaching Coulomb’s law.

In numerous studies the application of the molecular dynamics scheme based on reactive force field (ReaxFF) method has been proven effective in modeling catalytic behavior of metallic- organic compounds [1]. Recently, the method has been successfully applied for MOx (M=Cu, Fe, Mn, Ni) transition-metal oxides [2]. Yet, the problem arose during this analysis, since not all the force field parameters were available at the time. To bridge this gap, the force field for modeling mixed metal oxides had to be developed. For Mn-Fe bond, this was done within the work presented in a recent conference [3]. Here we establish the remaining two needed force field parameter sets (namely, Cu-Mn and Ni-Mn) and apply them to the problem of toluene adsorption on such catalyst mixed metal-oxide surfaces in order to verify their validity. The training set consisted of at least 10 crystal structures containing at minimum Ni-Mn-O or Cu-Mn-O atoms obtained from the Material project database [4]. The parameter training has been done using the in-home compiled version of the ReaxFF code. After training the force fields for geometry reproduction, the parameters were refined using the optimization by atom charges, comparing the ReaxFF values to those obtained for the respective structures using periodic crystal DFT codes implemented in Quantum Espresso [5] and Abinit [6]. [1] T. P. Senftle et al, npj Comput Mater, 2 15011 (2016). [2] M. Duplančić, V. Gomzi, A. Pintar, S. Kurajica, V. Tomašić, Ceramics Int. 47(3), 3108- 3121 (2021). [3] V. Gomzi, M. Duplančić, V. Tomašić Reactive force field optimization and MnFeO3 catalyst theoretical investigation, 18th Ruzicka Days, September 16–18, 2020 / Vukovar, Croatia. [4] (a) A. Jain, S.P. Ong et al, APL Materials, 1(1), 011002 (2013). (b) S. P. Ong et al, Comp. Mat. Sci., 68, 314–319 (2013). [5] (a) P. Giannozzi et. al., J.Phys.:Condens.Matter 21, 395502 (2009) (b) P Giannozzi et al, J.Phys.:Condens.Matter 29, 465901 (2017) (c) P. Giannozzi et al, J. Chem. Phys. 152, 154105 (2020). [6] X. Gonze et al, Comput. Phys. Commun. 248, 107042 (2020).

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 non-conservative 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-and-fading technique. Keywords: quasi-experiment, mechanical energy, teaching materials, teaching strategies

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.

In this study, our aim was to identify high school and university students’ postinstruction conceptions about the law of conservation of mechanical energy (LCME). A cross-sectional survey design was used. Firstly, a test consisting of 14 multiple-choice questions was developed. 23 physics teachers analysed the test and concluded that our questions are useful for measuring understanding about the LCME. Next, the test was administered to a convenient sample of high school and university students who had already received conventional instruction about the energy concept. The sample consisted of 138 students from the University of Zagreb (Croatia), and 115 high school students from two different schools in Sarajevo (Bosnia and Herzegovina). While the distribution of item difficulties was good, the reliability of test scores proved to be barely acceptable. Therefore, we primarily focused on analysing how frequently the students chose the individual distractors and drew corresponding conclusions about students’ conceptions. It has been shown that many students associate conservation of mechanical energy with certain surface features of physical problems (e.g., “pulley problems”), instead of reasoning about the processes a chosen system undergoes over time. Students often believe that mechanical energy is conserved even for phenomena in which air resistance cannot be neglected. Similarly, they sometimes do not recognize that most collisions of everyday objects necessarily include the conversion of mechanical energy into thermal energy. We could conclude that many students from all educational levels in Bosnia and

In the past decade, we have witnessed the emergence of a large number of different computer-based animations and simulations that have the goal to foster better learning of different physics topics. Past studies have shown many benefits of animations and simulations, but for their efficient usage it is very important that teachers are well educated in the teaching material and usage of selected visualizations. Furthermore, studies have proven that augmented reality technology has a potential to reduce cognitive load and improve the quality of physics lectures. Many of these visualizations are generally designed for targeted physics phenomena, and sometimes it is not easy to address specific students’ misconceptions. In this paper, we will present augmented reality animations and a simulation that can generally be useful for teaching about counterintuitive aspects of rolling motion, and specifically address students’ misconceptions about rolling friction and velocity in contact with the ground.

In this research papaer we presented the results of exploration of gender differences in conceptual understanding of rolling motion (velocities and work-energy principle). For this purpose, we have selected nine conceptual items and conducted experiment with 184 first year students at the Faculty of Chemical Engineering and Technology, University of Zagreb. Results show that male students significantly outperformed female students. We detected particularly large differences on items that tests knowledge of the rolling phenomena. Results of our research can help teachers to create lessons that are adapted to general student population.

Glutamic acid is one of the most important acids used in biosynthesis of proteins. In our study we measured FTIR spectrum of glutamic acid powder. The recorded spectrum is in accordance with well- known database spectrum of glutamic acid, but our extensive DFT calculations show that spectral band between 1900 and 3000 cm-1 does not originate from standard L-Glutamic acid conformation. We argue that this specific spectral band is associated with proton movement between the OH and NH2 groups. It is important to emphasize that our calculations show that one vibrational band corresponding to OH stretching strongly shifts by more than 1000 cm-1 to the lower part of vibrational spectrum. One of two OH groups is oriented towards NH2 group and its stretching band lowers due to proton movement. This kind of movement is lowering ground state energy of the Glutamic acid outside the dielectric medium, in which intermolecular hydrogen bonds flatten the structure and lower the energy. We give the typical conformation corresponding to this movement in graphical abstract.

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.

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.

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.

Poznato je da mnogi studenti imaju poteškoće s točnim predviđanjem utjecaja toplinskog rastezanja na izgled metalne ploče s kružnom pukotinom. Razgovori s profesorima pokazuju da bi izvor te poteškoće mogao proizaći iz činjenice da se studentske interne vizualizacije kod toplinskog rastezanja proizvoljnog objekta često svode na vizualizaciju promjene samo uzduž jedne dimenzije. U ovom smo istraživanju otkrili kako se studentski mentalni modeli o jednodimenzionalnom rastezanju mogu proširiti u svrhu pokretanja mentalnih simulacija o rastezanju uzduž dvije dimenzije. Proveli smo predtest-posttest kvazi-eksperiment sa 100 studenata u kontrolnoj grupi i 95 studenata u eksperimentalnoj grupi. Studenti kontrolne grupe sudjelovali su u tradicionalnoj nastavi s naglaskom na formalne prikaze dok su studenti u eksperimentalnoj grupi vođeni analogijom između zagrijavanja ravnog metalnog štapa i kružnog metalnog štapa iste duljine, pri čemu je unutarnja struktura štapa predstavljena oprugama. Rezultati su pokazali da su studenti iz eksperimentalne grupe bili značajno uspješniji u predviđanju učinaka toplinskog rastezanja, posebno u kontekstu objekata s rupama. Zaključak našeg istraživanja je da se analogije i rasuđivanje o ekstremnom slučaja može učinkovito koristiti za pomoć studentima kako bi pravilno primijenili svoje mentalne modele o jednodimenzionalnom rastezanju na situacije koje zahtijevaju rasuđivanje o rastezanju uzduž dvije dimenzije.

N, N-DMT molecule is known in many cultures as endogenous hallucinogen and most research has been directed towards the psychological effects or structural definition while molecular interactions in conditions of the human body are poorly understood. We have complemented past structural research of N, N-DMT and investigated molecular interactions of N, N-DMT in the environment of 0.1 M hydrochloric acid which is characteristic to gastric fluid. Experimentally we have measured spectra of N, N-DMT with IR and Raman techniques and computed individual vibrational frequencies at DFT–B3LYP level of theory. Furthermore we put N, N-DMT in solution similar to gastric fluid environment and experimentally detected shift in vibrational frequency which is confirmed in our calculation. Our theoretical model shows that the cause of this shift is cation- π bond between N, N-DMT and HCl in the vicinity of the benzene ring.