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The acceleration of a falling coffee filter released from rest is always much less than the free-fall acceleration of gravity, g. This is true even near the initial release, when the part of the drag force proportional to the velocity is negligible. This small acceleration occurs because there is a part of the drag force that is proportional to the acceleration. This part is called the added mass. The added mass is a large effect for falling coffee filters. Nesting the coffee filters does not change the added mass. The measured value of the added mass from the initial acceleration agrees with the theoretical value calculated for an ideal fluid. In experiments using a motion sensor or video analysis, it is easy to measure both the added mass and the steady-state drag force.

AAPT SM 21

Measuring the Added Mass of a Falling Coffee Filter

fluid

drag

added mass

coffee filter

experiment

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.


AAPT SM 20

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. 

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Join AAPT and Physics Educators worldwide in developing and strengthening your professional connections by attending the 2021 AAPT Virtual Summer Meeting. AAPT meetings are a great way to reflect on your teaching, recommit to best practices and re-energize your career with new research, products, and techniques.

Listen to internationally known plenary speakers, attend sessions, workshops, and special activities. Attending the virtual summer meeting is an excellent opportunity to share your expertise and learn from and network with leaders in the field.

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Swarmnotes is a new strategy for note-taking and coaching in an online classroom environment, in which students and the instructor collaboratively edit an online whiteboard. In this talk, we will demonstrate the logistics of Swarmnotes and demonstrate several uses of this flexible tool including Peer Instruction with multiple-choice, open-ended, or draw-a-diagram formats; handouts with gaps; derivations in which students take turns doing the next step; and notating-the-notes during and after class.

Swarmnotes for Live Collaborate Note-taking: Logistics and Uses

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A classic lab activity for electrostatics involves mapping out 2-D equipotentials on semi-conductive paper, allowing students to probe the shapes of electric fields and potentials. But what can be done for distance students or students who cannot attend a hands-on lab? To address this, we developed a graph-matching challenge in which students must lay out charges to produce a desired field and/or potential. The simulation activity runs entirely in Excel and features 3-D surface plots that are visually more stunning than the flat line drawings proposed in most textbooks, and arguably more evocative than the deliverables produced in the traditional lab. We discuss technical details and student reaction.

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Video-based graphical analysis homework problems

The electric field is one of the more abstract concepts taught in introductory physics. Introductory E&M courses often start by introducing Coulomb’s Law—an expression for the force between two point charges—before eventually defining the electric field as a ratio of the electric force to the charge on a “test charge”. This definition can result in some confusion among students; for example, students often have difficulty with the idea that the electric field is independent of the “test charge”. We decided to switch the order in which these topics are taught in a calculus-based introductory physics course: first introducing the electric field as the cause of electric forces, and later introducing the electric field caused by a point charge. We will share some pedagogical affordances of beginning E&M in this fashion as well as some observations from our initial implementation.

Teaching Electric Field before Coulomb’s Law

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Solving Kinematics Problems Using Kinematic Graphs

An Apparatus for the Lab of Uniform Circular Motion
Richard Guarino, Jingbo Ye
Department of Physics
Southern Methodist University

Uniform Circular Motion (UCM) is discussed in college physics. A lab that is commonly used to demonstrate the relationship between the centripetal force and the angular velocity usually involves a string. The string that connects the rotating object to a weight or a force sensor is turned 90 degrees by a pulley. This scheme has the problem that the string will twist and the pulley has friction. Utilizing the force and gyro sensors in a Pasco Force Sensor and with a custom rotor, we constructed a UCM lab with precision measurement results. A photogate is used to double check the angular velocity measured by the gyro sensor. This double measurement of the same quantity provides students with an example and training of calibration and cross-check in scientific work. We will present the design and performance of this lab, and share the lab manual with interested fellow lab instructors. 


An Apparatus for the Lab of Uniform Circular Motion

Many newly reformed introductory physics laboratory courses prioritize student engagement with scientific practices, in line with a significant body of PER research that suggests these courses often do not adequately enhance students’ conceptual knowledge. However, is it possible for introductory physics labs to focus on student engagement with scientific practices AND generation of conceptual knowledge simultaneously? In this presentation, I discuss how our Introductory Physics for Life Sciences (IPLS) lab instructional team refined existing evidence-based instructional strategies and curricular activities to elicit students’ simultaneous engagement in scientific practices and the generation and utilization of new conceptual knowledge during investigations. We show how these refinements resulted in students collaboratively generating conceptual mechanistic knowledge of complex biophysical systems and using this knowledge in open-ended experiments to build scientific models of related scientific phenomena. These examples provide evidence that physics lab courses can engage students with scientific practices and conceptual learning simultaneously.

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Measuring the Added Mass of a Falling Coffee Filter

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