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Damped harmonic oscillation: Linear or quadratic drag force?
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| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 87 (No. 11) |
| Halaman | : | 910-914 |
| Abstrak | : | Harmonic oscillation damped by quadratic drag force is rarely found in physics textbooks. We present typical characteristics of the phenomenon and an analytical tool for the experimental determination of the resistance regime. The measurement is simulated using randomly generated amplitudes with different types of statistical and systematic errors. Their impact on the process of distinguishing between the linear and quadratic regimes and on the measured damping parameters is studied. |
Using classroom observations to evaluate science teaching: Implications of lesson sampling for measuring science teaching effectiveness across lesson types
| Pengarang | : | Jamie N. Mikeska, Steven Holtzman, Daniel F. McCaffrey, Shuangshuang Liu, Tamara Shattuck |
| Nama Majalah/Jurnal | : | Science Education |
| Volume / Edisi | : | 103 (No. 1) |
| Halaman | : | 123-144 |
| Abstrak | : | Despite the prevalent use of observational measures in teacher evaluation systems, research has only recently begun to take into account how aspects of the instructional environment and lesson sampling design may interact with teachers’ scores on these measures. Instead, one assumption guiding current evaluation systems is that the variation in teachers’ instructional practices captured by the lessons sampled is a valid measure of their teaching quality. Our study investigates this assumption by examining whether scores from observational measures of science teachers’ instructional practices vary depending on lesson type. Results show that science teachers’ scores on certain observational measures vary across lab and nonlab lessons, suggesting that the claims one can make about science teaching effectiveness are dependent on the particular types of lessons observed. Given the increasing prominence and use of observational measures within evaluation systems, it is imperative to ensure that the observed lessons adequately represent variation in a teacher’s practice and are not subject to undue instability from the types of lessons included in the sample, especially in science where there are clear distinctions in the instructional practices teachers employ across lab and nonlab lessons. Implications for measuring science teaching quality are discussed. |
Applying the ambitious science teaching framework in undergraduate biology: Responsive talk moves that support explanatory rigor
| Pengarang | : | Anna S. Grinath, Sherry A. Southerland |
| Nama Majalah/Jurnal | : | Science Education |
| Volume / Edisi | : | 103 (No. 1) |
| Halaman | : | 92-122 |
| Abstrak | : | Orchestrating opportunities for students to engage in scientific talk in the classroom is challenging for most teachers and even more so for novice teaching assistants (TAs) who typically instruct introductory science laboratories at the postsecondary level. This study was designed to understand how TA moves are related to instances of scientific discourse in the classroom (meaning discourse that includes a high degree of explanatory rigor). For this, we examined the enactment of a planned “elicitation discussion” that took place in 26 sections of a general biology laboratory for nonscience majors. Our research was driven by two-related questions: What patterns of discourse emerged? What TA discursive moves were related to high levels of explanatory rigor in student talk? Using conversation analysis, four distinct patterns of discourse were identified, each representing different levels of explanatory rigor. Regression analysis revealed that the type of question the TA used to initiate classroom talk was not significantly related to the students’ explanatory rigor. Rather, the most important aspect of TA talk for elevating the explanatory rigor of student discourse was TA responses to student contributions to TA's initiating questions. The implications of these findings for TA professional development are discussed. |
Why pushing a bell does not produce a sound
| Pengarang | : | Loris Ferrari |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 87 (No. 11) |
| Halaman | : | 901-909 |
| Abstrak | : | The difference between “beating” and “pushing” results in the perception that a push just makes an object move as a whole, while a beat also produces a sound. Through a detailed analysis of the physics underlying such everyday experiences, we identify the strength, the duration, and the softness of the applied contact force as the main (measurable) characteristics that mark such a difference. The strength determines the final velocity Δv achieved by the body. The duration 2τ corresponds to the time τ? the sound takes to cross the body. The softness γ (a positive exponent) results from the shape in time of the contact force. These three elements make up the formula for the intensity of the sound produced. The relevant role of the softness is stressed and specific values are calculated for a thin metallic bar, which is chosen as the simplest possible model system. |
Persistence of the two-worlds pitfall: Learning to teach within and across settings
| Pengarang | : | Melissa Braaten |
| Nama Majalah/Jurnal | : | Science Education |
| Volume / Edisi | : | 103 (No. 1) |
| Halaman | : | 61-91 |
| Abstrak | : | Learning to teach within and across the settings of teacher education coursework and field experience in local schools is subject to the “two-worlds pitfall,” where practices, norms, expectations, tools, and other aspects of teaching can be jarringly different. This remains an ever-present dilemma for preservice teachers, their teacher educators, and their school-based mentors. This collective case study follows two cohorts of secondary science teacher candidates (22 in total) through their field experiences in local schools to understand how they reorganized, repurposed, and retooled practice as they worked on noticing and responding to students using ambitious science teaching principles and practices. Analysis highlights how instructional experiences in K–12 classrooms and relationships with mentors afforded and constrained preservice teachers’ efforts to recontextualize ambitious science teaching practices in the status quo science teaching contexts of local schools. Recommendations for increasing permeability between the two worlds of teacher preparation are included. |
Grappling with racism as foundational practice of science teaching
| Pengarang | : | Manali J. Sheth |
| Nama Majalah/Jurnal | : | Science Education |
| Volume / Edisi | : | 103 (No. 1) |
| Halaman | : | 37-60 |
| Abstrak | : | While current science teacher education frameworks designed to support high-quality teaching have the potential to promote equitable science learning, they do not substantively engage with how racism organizes science teaching and learning. In this critical qualitative inquiry grounded in critical race theory and sociopolitical perspectives on teaching and learning, I analyzed the contradictions that emerged in science teaching practices that were both intended to support Student of Color science learning and engaged science-specific colorblind ideologies. The critical race theory analysis demonstrated how science teaching practices such as connecting to students’ experiences, creating interests in science, representing scientists as role models, and scaffolding doing science maintain unequal racialized power relations between students and science when historical and contemporary legacies of racism are not directly confronted. I also propose a science teaching practice of “grappling with racism” as a possible transformative solution to disrupt racism in and through science teaching. |
Physical analysis and optimization of electromagnetic coilgun launch systems
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 87 (No. 11) |
| Halaman | : | 894-900 |
| Abstrak | : | Coilguns are one of the most widely used projectile launch systems using electromagnetic force. The ideal coilgun would propel a projectile with maximum velocity while also having a high power efficiency. The physics of coilguns is well understood; however, optimizing the coilgun design is much more difficult, as it requires the consideration of the parameters of every component of the system, such as the coil, projectile, and power supply. In this paper, electromagnetism, kinematics, and electrical circuit theory are employed to analytically describe the operations of a coilgun with permanent magnetic projectiles. These analytical equations are then implemented using mathematical programs. Coilguns with distinct design parameters and current profiles can be tested numerically to quickly find the optimal combinations to achieve the maximum velocity or power efficiency. The results are presented and measurements are utilized to verify the predictions. |
Demonstrating the elliptical orbit of Mars using naked eye data
| Pengarang | : | Kevin Krisciunas |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 87 (No. 11) |
| Halaman | : | 885-893 |
| Abstrak | : | The discovery of Kepler's three laws of planetary motion served as a significant motivation to Newton to find the gravitational force law and explain why motion in an inverse square law force field produces orbits (or trajectories) that are conic sections. Kepler's discovery that Mars' orbit is an ellipse is one of the most significant in the history of astronomy. It relied on Tycho Brahe's observations, which were the most accurate data ever attained at that time. In this paper, we present an analysis of positional measurements carried out during two observing periods of ∼400 days centered on the 2016 and 2018 oppositions of Mars. Our observations were made with the naked eye and a simple cross staff. If we assume an elliptical orbit of Mars and simplify matters by adopting a circular orbit for the Earth, the data of the 2016 opposition indicate that the eccentricity of Mars' orbit is 0.093 ± 0.012. This is equal to the modern accepted value, but with a larger uncertainty. By adopting a more robust model that uses an ellipse for the Earth as well, we obtain a better fit, with an RMS residual of ±7.5 arc min for the ecliptic longitudes. The data of the 2018 opposition must be fit with an ellipse for Mars and the Earth. |
Were getting somewhere: Development and implementation of a framework for the analysis of productive science discourse
| Pengarang | : | Michener, Catherine J.,Suh, Sora |
| Nama Majalah/Jurnal | : | Science Education |
| Volume / Edisi | : | 103 (No. 1) |
| Halaman | : | 5-36 |
| Abstrak | : | Sense-making and argumentation are two common ways to frame student discourse. The former emphasizes the process of students coming to an understanding, the latter the logical and rhetorical structure of the product. When we investigated the discourse of two groups of preservice science teachers in an environment that fosters productive disciplinary engagement, we found that elements of both sense-making and argumentation pervaded the discourse as the preservice teachers engaged in the scientific practice of developing an explanation of a complex phenomenon. We have developed a framework based on, but extending that of Toulmin that allowed us to capture the to-and-fro nature of the development of an explanation by using elements of argumentation and sense-making as well as transactivity. Using the framework we were able to characterize almost all utterances of the 40-min discourse of both groups. Both groups arrived at a similar point of conceptual convergence, even though the interactions that took place during the activity were of quite a different nature. We detail the affordances of our framework and contrast them with those of purely argumentation-based frameworks. |
Student and instructor framing in upper-division physics
| Pengarang | : | Deepa N. Chari |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 87 (No. 11) |
| Halaman | : | 875-884 |
| Abstrak | : | Upper-division physics students spend much of their time solving problems. In addition to their basic skills and background, their epistemic framing can form an important part of their ability to learn physics from these problems. Encouraging students to move toward productive framing may help them solve problems. Thus, an instructor should understand the specifics of how students have framed a problem and understand how her interaction with the students will impact that framing. In this study, we investigate epistemic framing of students in problem solving situations where math is applied to physics. To analyze the frames and changes in frames, we develop and use a two axis framework involving conceptual and algorithmic physics and math. We examine student and instructor framing and the interactions of these frames over a range of problems in an upper-division electromagnetic field course. Within interactions, students and instructors generally follow each others' leads in framing. |