Vibrational Motion

Originally posted November 15, 2021 on FB

Hi all, today I continue with vibrational motion. Do not forget to like the post when you finish reading (who knows, maybe you will even love it 🙂 For many years I taught vibrational motion of a simple pendulum as vibrational motion, focusing on the tangential components of the net force and acceleration. It did not occur to me, that it was also circular motion at changing speed. Many generations of my students never learned that the acceleration fo the pendulum bob is not along the tangent to the circle and is not towards the center of the circle but has a variable directions that can be determined by drawing a good force diagram (forces to scale) and even better – by drawing a good motion diagram. Here is the activity that allows your students to figure it out. Only a small percentage of physics graduate students can draw the direction of acceleration of a pendulum at different points of the arc (research by late Lillian McDermott). Your students will be able to! The answers to the questions in the activity are in the textbook on page 297. If you need them, I can post as a separate post. If you read to the end, you know what to do next!

About the Author

Eugenia Etkina

Eugenia Etkina is a Distinguished Professor at Rutgers, the State University Of New Jersey. She holds a PhD in physics education from Moscow State Pedagogical University and has more than 39 years of experience teaching physics at high school and university levels. She is a Recipient of the 2014 Millikan Medal of the American Association of Physics Teachers (AAPT), awarded to educators who have made significant contributions to teaching physics, and is a fellow of the AAPT.

Professor Etkina designed and now coordinates one of the largest programs in physics teacher preparation in the United States, conducts professional development for high school and university physics instructors, and participates in reforms to the undergraduate physics courses.

In 1993 she developed a system in which students learn physics using processes that mirror scientific practice which was later enriched by her collaboration with A. Van Heuvelen. That system, called the Investigative Science Learning Environment (ISLE) approach, can be used in a physics course of any level (from middle school to graduate coursework). It engages students in learning physics by practicing it, and improves their well-being. The ISLE approach serves as the basis for the textbook “College Physics: Explore and Apply” and supporting Active Learning Guide and Instructor Guide that are used in many universities and high schools for teaching algebra-based physics courses, especially Advance Placement Physics course.

Since 2000, Professor Etkina has conducted over 140 workshops for physics instructors. She is an active researcher who has published over 100 peer-refereed articles.

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