Center for Instructional
Innovation and Assessment


Andrew Boudreaux
Science Education Team
Stephanie Treneer
Andrew Boudreaux
Department of Physics & Astronomy

Implementation Notes

Designing Learning Experiences for the Introductory Physics Lab

Within and throughout the Physics instructional sequence, a set of common pedagogical themes have been used to guide the design of student learning experiences more specifically. These themes reflect key findings from the body of research on learning and teaching described in the Portfolio. We have drawn particular inspiration from a number of nationally disseminated research-based curricula, including Tutorials in Introductory Physics, developed at the University of Washington (Shaffer et al., 2000) and Physics and Everyday Thinking, developed at San Diego State University (Goldberg et al., 2008). For practical reasons, these curricula are not well suited to our local context, but their overall approach to inquiry-based learning has strongly influenced our work.

Coherent implementation of our guiding pedagogical themes has come about through iterative modification of the labs based on extensive classroom use with students. Below we describe the role of each theme in the lab curriculum, with illustrations from specific labs.

Learning targets that are specific and public. Research-informed best teaching practices indicate that clear, up-front statements of the specific goals of learning activities help students focus on and achieve those goals (Lachlan-Haché & Castro, 2015). Instead of keeping the target ideas hidden, as sometimes occurs in traditional physics instruction, the first page of each lab presents them clearly, in language that students can understand. (Table 2 presents the learning targets for selected labs.) Different portions of the lab are keyed explicitly to specific learning targets, letting students know what they should take away from each activity. Finally, each lab ends with a reflection, in which students select one of the learning targets to revisit in some detail, describing where their thinking started, what they now understand, and the intellectual steps through which their understanding of that learning target changed or deepened.

Table 2. Selected labs and associated content learning targets

Lab Content Learning Targets

Mechanics 1: Concepts of motion

  • Draw and interpret x vs t and v vs t graphs.
  • Relate v, Δx, and Δt.
  • Relate a, Δv, and Δt
  • Translate between graphs, equations, and verbal descriptions of motion.
  • Apply equations for motion with const. accel. to make quantitative predictions.

Mechanics 5: Newton's 3rd law and the static force

  • Explain and apply Newton's third law.
  • Use ΣF = 0 to determine static friction force from knowledge of the other forces acting on the object.
  • Distinguish the actual friction force from the maximum possible static friction force.
  • Apply mathematical model (fmax = μN) to relate the maximum possible static friction force in a given system to the characteristics of the system.
  • Determine the coefficient of static friction experimentally.

E&M 1: Charge

  • Explain the observational basis for different types of electric charge.
  • Explain the observational basis for classifying materials as conductors or insulators.
  • Account for the interaction between charged and uncharged objects.
  • Apply a conceptual model for electric charge to explain the outcome of experiments using simple materials (rods, metal balls, etc.).
  • Explain charging by induction.

Guided questions that help students build lines of reasoning. Rather than "turning students loose" in open-ended investigations, the labs define the scope of inquiry by providing a specific physical context and a sequence of questions to guide students' explorations. The questions serve as stepping stones in a reasoning pathway. In some cases, students are guided through inductive reasoning, in which they synthesize multiple, specific observations to articulate a more general pattern or rule. Other activities take students through a deductive pathway, in which they apply a general principle to make a prediction about a case at hand. For example, in the forces lab, students are asked to predict the shape of a velocity vs time graph when a cart coasting along a low-friction track is given a brief backwards tap by a hand. They must apply knowledge of Newtons 2nd law - that an unbalanced force causes an object's velocity to change - together with an understanding of the specific horizontal forces acting on the cart throughout the scenario. Prediction in hand, students are prompted to check their thinking by conducting the experiment, and through discussion with their lab partners, to resolve any discrepancies between their predictions and observations. For guided steps such as these to be effective, we have found that careful attention to the spacing of the steps is required. Questions that are too far apart can lose students, while questions too close together can undermine engagement and lead to answer making at the expense of sense making.

Regular formative feedback. The primary mechanism for formative assessment in the labs are the discussions between students and instructors. TA's listen and ask questions first, to gauge where students are in their learning, so that feedback can be tailored to the specific needs of the students. A more formal opportunity for formative feedback occurs in the checkout discussion. After students have collaboratively reviewed their prelab, they are prompted to call over their instructor and explain their current understanding and how their thinking has changed. Students must document their revised thinking by annotating their prelab in writing, using colored pencil. Figure 1 shows an example of a revised student prelab.

Bouncy Ball

Figure 1. An example of a revised student prelab. During lab, students collaborate to review their original prelab explanations, identifying productive and problematic aspects of their reasoning. (Above, the student's original response is in black, with revisions in red and green.) The group then explains their current understanding to an instructor in a "check-out discussion."

Explicit targeting of known learning difficulties. As discussed earlier, research in physics education has identified obstacles to the learning of specific content that arise commonly, for many individual learners, and that can be persistent. For example, even after studying Newton's 3rd law, many students will claim that when a large and a small object collide, the magnitude of the mutual forces they exert on one another are different (Elby, 2001). (According to the 3rd law, those forces must have identical magnitudes.) Such difficulties can short circuit the guided learning pathways described above. Following best practices established in the physics education research literature, the labs try to bring these difficulties out into the open, where students can examine and address them. This approach can seem counter-intuitive to instructors not familiar with inquiry-based learning, in that confusion is being deliberately introduced into the learning environment.

In the 3rd law lab, after students have conducted experiments and drawn conclusions, they consider a fictitious dialogue, in which one of the "students" argues that "during a collision, a bigger object ought to exert more force on a smaller object than the smaller exerts on the bigger." Students are asked to evaluate this idea, and to reconcile it with the formal statement of the 3rd law. In this exercise, students recognize that the fictitious statement is inaccurate, and explain that it is the effect of the force that differs between the two carts, rather than the force itself. (The larger cart experiences a smaller acceleration, even though the collision forces have the same magnitude.)

Practical considerations. We have designed our lab curriculum such that it can be incorporated into an existing, otherwise traditional introductory physics course. This was important because our faculty rotate in and out of the lecture portion of the course. Labs meet weekly in sections of ~25 students, covering the foundational concepts in a standard, year-long introductory calculus-based physics sequence. We have developed over 20 labs in all, in mechanics (Kinematics in One Dimension, Motion in Two Dimensions, Forces and Newton's 2nd Law, etc.), electricity and magnetism (A Model for Charge, Electric Field, Electric Potential Difference, etc.), and waves and optics (Mechanical Waves, Physical Optics, etc.). Most labs assume that students have been exposed to relevant content through a brief introduction in lecture, or reading the textbook, but do not assume deep understanding or computational facility. Students print all written lab materials from the course website (prelab, lab worksheet, and lab homework). In addition to the 2-hour lab section, students spend about 2 hours out of lab on the prelab and homework.

Undergraduate physics majors serve as the primary lab instructors. They attend a weekly, 90-minute preparation meeting led by a faculty member, and spend approximately 2 hours per lab section grading students' written work. Thus a TA with two lab sections has a total time commitment of about 10 hours per week. One TA with prior experience usually works an additional 2 hours to set up and take down equipment. The labs make use of standard introductory physics lab apparatus.

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