In the development of Physics 131, we have been working backwards: refining the course starting with the last unit on entropy and then moving towards the start of the semester. Due to this approach, our first two units on the mathematical foundations of physics and forces are now our weakest two units. Moreover, Unit 3 – Forces and… covers a LOT of material: impulse, work, and torque. One of our (many!) goals for the summer is then to revamp these first two units – hopefully making the labs a more valuable experience at the same time. One of the big guiding principles of this revamp is to use the idea of expansive framing described in Engle et al [1].
In expansive framing, students return to the same fundamental concept multiple times and using multiple concepts to develop a more holistic understanding of some complex phenomenon. This idea is used in a second-semester introductory physics for life sciences course on electricity and magnetism by Crouch et al [2] wherein they return to the idea of the cell membrane under several contexts including electric potential and field between two plates as well as in circuits. We at UMass are actually already using such a technique in our last unit on entropy where we use a lab to explore the free expansion. Through this lab, which we return to several times over a week, we explore many entropy’s basic principles.
In these introductory units, we already have a great context to which we could repeatedly return: a lab exploring the mechanics of a human jump based upon a Kin 408 lab at University of Southern California [3]. In our courses, 16% of students are majoring in kinesiology with a good deal more interested in the health sciences. This particular lab measures human motion using a force plate which is a common piece of clinical equipment [4]. Therefore, this context has intrinsic interest to our students.
The plan therefore is to use this (very long!) lab as a touchstone throughout the first two units: we will begin the lab right at the start of the semester using it as a complex and real-life example of understanding motion graphs (which we can create using standard motion sensors). As the unit progresses, we can explore the same motion in the context of Newton’s 2nd Law right after exploring the elevator as the concepts are the same. Newton’s 3rd Law will even come in to play as we look in to the fact that we are actually measuring the person pressing down on the scale which is, of course, equal to the force the scale pushes up on the person.
In addition to providing a expansive framing context for the exploration of motion graphs and Newton’s Laws, this structure will allow us to spread this long lab out over several weeks giving students time to digest each portion. Moreover, this structure will integrate the ideas of impulse directly into our discussion on forces which reduces the cognitive load in preparing for Unit 3 which, since we are simultaneously moving work to Unit 4 – Energy, will now just be static torque.
Watch this space to see how these changes move forward!