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Students know that a simple harmonic oscillator (SHO) has a ‘resonance curve’, and some students even know how to label the axes of a plot showing that resonance curve. The frequency (and amplitude) of a sinusoidal drive force are the main independent variables, and the steady-state amplitude of the SHO’s response is the main dependent variable. But a simple modification to a mechanical SHO can change it from ‘direct drive’ to ‘parametric drive’, and this subtle change has dramatic consequences. First of all, parametric resonance occurs when the drive frequency is not at the SHO’s natural frequency, but nearly _double_ that frequency. Next, there no longer emerges any steady-state amplitude of response, and the right dependent variable to measure is the rate of _exponential growth_ (or decay) of the system’s oscillations. There is also a _threshold amplitude_ for the drive required to give any growth in the response. This presentation features a torsional SHO with a non-contact parametric drive, and shows theoretical predictions and experimental data for its performance. Finally, we connect this parametric drive of a mechanical SHO to some glamorous applications of parametric excitation in modern physics.

AAPT SM 20

What is &#39;parametric drive&#39; of a simple harmonic oscillator?

parametric excitation

resonance

The 2020 AAPT Virtual Summer Meeting brought together physics educators from around the globe to learn about the latest in physics theory, research methodology and education from leaders in their field. The program featured plenary speakers, sessions, workshops and many special activities.

For more information please visit the 2020 AAPT Virtual Summer Meeting page at: https://www.aapt.org/Conferences/SM2020/index.cfm.


The 2020 AAPT Virtual Summer Meeting brought together physics educators from around the globe to learn about the latest in physics theory, research methodology and education from leaders in their field. 

What is 'parametric drive' of a simple harmonic oscillator?

technical paper

We have co-authored a new textbook, “Experimental Physics: Principles and Practice for the Laboratory”, inspired by the 2014 AAPT report “Recommendations for the Undergraduate Physics Laboratory Curriculum”. We discuss the philosophy and organization of the book, and the support that will be offered for remote education, assuming it is needed this year. We also detail aspects that differ from previous texts. For example, ours is written by a team of 17 research-active authors, allowing authoritative writing about techniques relevant to all major areas of physics; detailed instructor manuals are included so that you can confidently teach outside your area of expertise. As of abstract submission, development of remote instruction materials is only beginning. They will include a variety of approaches, such as modifications of some experiments so they can be done at home using modestly priced kits, as well as “choose your own adventure”-style video walkthroughs of other experiments.

A new advanced lab textbook, with support for remote instruction

What happens to aspiring engineers who do not pass their introductory mechanics class? At UIUC, approximately 11 percent of introductory mechanics engineering students earn a D, F, or W. Just 31 percent of these students go on to earn an engineering degree, compared with the 87 percent of students who pass the course on their first attempt. While most students who perform poorly in their introductory physics class choose a non-engineering major or leave the university altogether, there is a unique subset of initially struggling students who choose to persist in an engineering major. We interviewed engineering seniors in this group to learn about their experiences as engineering students who overcame an initial setback. In this talk, we will discuss big-picture outcomes for students who retake this fundamental course as well as insights into the difficulties some students face and what resources may help them succeed.

When the Gatekeeper Says No: Mechanics Students' Resilience and Success

We discuss a simple and novel method due to Müller-Plathe to compute the thermal conductivity and viscosity in a molecular dynamics simulation. The method is easy to explain and provides insight into nonequilibrium steady state processes. The method is discussed in the added chapter to the forthcoming second edition of our text on thermal physics.

Molecular dynamics calculation of thermal conductivity and viscosity

We address two major issues in the methods PER has historically used to interpret student outcomes on research based assessments (e.g., the FCI). First, PER has historically used normalized learning gain (g) as a normalizing factor to interpret student outcome scores. This is problematic because g has no statistical basis and is biased in favor of high pre-score groups. Second, instructors have been comparing their student outcomes to those in the published literature. This is problematic because the published literature overrepresents outcomes from courses in highly-selective institutions. In this talk we will offer two alternative methods for interpreting student outcomes based on our analysis of a large-scale dataset with representation across the spectrum of institution types. Specifically, we recommend interpreting student outcomes using either a scatter-plot of a large-scale course pretest and posttest scores or an effect size measure (e.g., Cohen’s d of Hedges g).

More representative and less biased methods for interpreting student outcome data

Teaching labs during a pandemic:  Lessons from Spring 2020 and an outlook for the future

The presenters will describe a course that was developed to explore themes related to science and religion. The course — “Science and Religion: Anomalies and Miracles” — was team taught by professors of physics and religious studies, and was designed around a unifying question that motivated the course content and discussions: Historically, how have practitioners of science and religion dealt with unexplained or unexpected events? How do particular worldviews inform the way they receive, interpret, or reject novel ideas? We will present a big-picture overview of the course content, as well as some specific lessons and discussions that illustrate the unique approaches that the team-taught structure permitted. We will also discuss the results of a student survey about the course and explore what students described as the enduring understandings, more than ten years later, that they retained from the experience.

Anomalies and Miracles: Revisiting an Undergraduate Science and Religion Course

Like many institutions during Spring 2020, our university quickly switched to online instruction, and we will share our experiences. We wrestled with how to turn the remaining labs into online labs and tried different methods in our Introductory Physics 1 and Physics 2 Labs. We also deliberated on whether or not to reduce the number of labs required for the semester and how to keep the Teaching Assistants employed. Additionally, we made plans to improve the quality of our online labs in the possibility of a return to virtual instruction in the Fall 2020 semester.

Online Introductory Physics Labs During Covid-19

This talk describes some events designed to share culture among students and faculty. In order to enhance the participation of women and minoritized students and to elevate the experiences of all students, we must find ways to allow students to bring their whole selves into their studies. The illusion that Physics has no culture is damaging especially those who do not feel welcome. By discussing culture and sharing our culture we can strengthen connections between students and faculty.

Cultural Exchange Events

Given the development of the Covid-19 global pandemic during the Spring semester of 2020, proctoring an in person, comprehensive, written final was no longer an option. While I considered the alternatives, I began to question the learning goals of the course and the value of a traditional final exam. I want my students to continue to think about the course material outside the classroom, to gain a deeper appreciation of the subject, and to reflect on the course as a meaningful and influential life experience. To bring meaning, there must be elements of community, civic responsibility, and personal growth. To that end, students were matched with local seniors, those more vulnerable to loneliness due to the pandemic. They met with their senior via Zoom to discuss connections between course material and the current social, economic, and political context as well as the current coronavirus pandemic and public health in general.

Covid-19: An Opportunity to Drive the Undergraduate Introductory Physics Curriculum toward Change

Classes with multiple teachers is a challenging way for teaching science. The hard part is, teachers have mostly chosen their teaching styles, and blending teaching styles after years of development can be daunting. This limits opportunities to try new approaches. However, co-teaching provides the opportunity to teach with different approaches and group work strategies, which can be a little hard but exciting. We decided to follow the same lesson plans, lab tools, quizzes and grading strategy for three introductory calculus-based mechanics classes for one quarter, including combining the classes in our Learning Management System, Canvas. We were all equally responsible as the course instructor in our in-class instruction and our online presence as well. In this experience, we improved our teaching and collaboration skills and students learned how to engage in co-taught a class with many students and multiple teachers.

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What is 'parametric drive' of a simple harmonic oscillator?

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