Was the moon landing faked? (Phys101 PCOs, weeks 4-6)

(This is the second post in a semester long series about the pre-class overheads, or PCOs, Joss Ives and I use as discussion pieces in Physics 101, a large-scale first-year physics course. The intent of these posts is to create a record of the images we choose and of the thoughts behind our choices. See also the first post in the series.)

A new component of Physics 101 for students this semester is the inclusion of Learning Objects as part of their coursework. From the course material, a Learning Object is “A resource developed by you [the student] that can be used by other students to understand and explore a question or concept in Physics 101.” An initiative of Simon Bates and Firas Moosvi, and building upon previous work using PeerWise in introductory physics courses (see the paper here), Learning Objects provide an opportunity for students to engage more deeply with the material by developing their own content. The most typical example of a resource is a simple multiple choice question, while more complex Learning Objects that have been submitted include Prezis and YouTube videos. Throughout the semester, each student must create at least two Learning Objects. Many of these student creations are featured on the course website, available for other students to learn from, and some of the best ones are featured in lecture and recitation sessions.

In terms of our plan to begin classes with peer-discussion overheads, these Learning Objects provide us with a great opportunity to bring student-generated content into the lecture. One hypothesis we have is that the student-generated content may be more interesting for students, which might result in better discussions. So, we make an effort to incorporate this content into the lecture, both in the pre-class overhead and throughout. In the weeks covered in this post, we used our first pre-class overheads that were inspired by student submitted Learning Objects.

Through these three weeks of the semester, the topics covered included periodic motion and simple harmonic motion in terms of masses on springs and simple pendulums.

Week 4

A sunset at picturesque Kitsilano beach, Vancouver.

A sunset at picturesque Kitsilano beach, Vancouver. Can you find at least 3 things that undergo some sort of period motion?
(Copyright User:Mathew5000 / Wikimedia Commons / CC-BY-SA-3.0)

To begin our descent into periodic motion (to become simple harmonic motion and, ultimately, the study of waves), we started class with an iconic Vancouver image: a sunset viewed from Kitsilano beach. Since some of the discussions hadn’t been going so well, Joss and I decided to give the class more structure for this task. In previous weeks Joss encouraged the class to discuss the interesting physics that might be going on in the image. For this picture, we decided to ask something more straightforward: Find three things in the image that undergo periodic motion. Some of the examples that came up in the discussion included: hearts beating, propellors on the large tankers, the sun’s motion across the sky, and the tides.

In the second class of the week, we began not with an image, but with a running PhET Masses & Springs simulation. Joss set up the simulation with a variety of different masses on springs and including some friction. For the first few minutes of class, we let the simulation run (let the springs oscillate up and down) while the students were tasked with observing interesting points about the systems. A particular point that Joss discussed with the whole class was how the thermal energy of the system was steadily increasing, while the mechanical energy was decreasing. This friction in the mass-spring system was not something we had yet encountered in the class material, so this provided some foreshadowing of upcoming damping material.

Week 5

In this week, for the first time, we used content inspired by a student-submitted Learning Object as our pre-class discussion piece. The Learning Object was based on this YouTube video of astronauts on the moon. In the video and in the student’s learning object, the motion of a swinging piece of rope is analyzed by approximating it as a simple pendulum. By measuring the period of oscillations, estimating the effective length of the pendulum, and using the equation for the period of a pendulum, it was concluded that the astronauts were indeed in an environment with a gravitational force  that is about one-sixth that as on Earth (consistent with it being the moon).

Based on this Learning Object, we put up a cobbled-together image, copy and pasting a pendulum onto a background of the moon’s surface. The specific task we asked of students was to come up with a description of how the period of the pendulum changes (as compared to on the Earth) that did not rely on simply plugging the new gravitational acceleration into the equation. In this way, we tried to promote some conceptual understanding.

On the second day of the week, we stepped back from simple harmonic motion to buoyancy (which was good practice for the students since their first midterm was coming up), and used an image of a schematic cross-section of a submarine. On the cross-section were labelled the ballast tanks and tanks of compressed air. For the peer discussion related to this image, we asked students to try to explain how a submarine could control its depth in the water. It is a complicated question, but most students were able to correctly identify that the submarine takes on/releases water from its ballast tanks in order to adjust its average density, thus causing it to rise or sink in the water.

Week 6

For the first class of this week, we again revisited material from earlier weeks in the course. This time, we showed an image of someone siphoning gasoline and asked the students to try and describe how the siphon works. A siphon is a little counterintuitive, in that the fluid actually has to travel up before going down and out. A few factors come into play, including continuity and Bernoulli’s equation. Perhaps the best intuition for me came from thinking about Bernoulli’s equation: Unless the highest point of the siphon is too high (recall the maximum length of Superman’s straw), the siphon works just like a pipe going straight down from a higher area to a lower area, because from the point of view of Bernoulli’s equation, the path the fluid takes doesn’t matter.

To begin the second class of the week, we used a very neat video that was part of a Learning Object built on the TED-Ed website:

Each billiard ball’s period differs due the different oscillation lengths. The result is a mesmerizing demonstration of simple harmonic motion.

Notes about task structure and engagement

So far, we have found that more structured tasks have been more successful in getting students engaged. This enhanced engagement hasn’t necessarily translated into a full classroom discussion, however, as students have still been reluctant to share their thoughts with the entire room. However, it may be that students participating in peer discussions about the image and students reporting their thoughts to the entire class are two entirely separate things; the fact that they are not participating in the latter doesn’t necessarily mean that they’re missing out on the learning opportunity. In future weeks, we will continue to tweak our presentation of these images with these thoughts in mind.

Questions for the reader

  • What images would you suggest, related to the images or topics described above?
  • Which image do you think generated the most interest?
  • Do you think its worthwhile to add these to the course content?
  • How might you promote class-wide discussions in large-scale courses?
  • Are class-wide discussions important in large-scale courses, or are peer interactions enough for students to be properly engaged?

One comment

  1. […] a record of the images we choose and of the thoughts behind our choices. See also the first and second posts in the […]

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