Author: geoff

Whiteboarding the projectile-motion problems has the potential to be less engaging because many students find these problems easy because they are an application of existing models which which they are familiar. To keep whiteboarding interesting, I introduced the Mistake Game today. Students came up with several believable mistakes to hide on their whiteboards. Here is one where they didn’t use the components of the velocity:

I also want to share this whiteboard which presented the independent of the horizontal and vertical motion so clearly:

  ##pmm ##whiteboarding  

We have our own unique twist on the traditional monkey-and-hunter demonstration. My colleague developed a narrative that focuses on Anti-Curious George:

The story is that Anti-Curious George was produced a Fermilab where they can make antimatter. (I usually get on a bit of a tangent about Fermilab, particle colliders, and high-energy physics.) Anti-Curious George is curious like his counterpart, but unlike his counterpart, he is not basically good, he is evil. Our job is to capture him by shooting him with the tranquilizer gun. We share that we know from careful observation that Anti-Curious George will drop from the tree when we fire our gun. The question posed to the students is where to aim. Very few (usually none) predict that we should aim right at Anti-Curious George.

After the surprising result of the demonstration, I challenge the students to explain conceptually why we should aim right at the target. This is not easy and it was a few years before I developed a solid conceptual explanation that students would grasp. I also refer them to a problem in the text in which they can prove algebraically why this works. (First time I’ve referenced the text this year.) Tomorrow, we will discuss the outcome of this conceptually and algebraic challenge!

Today I did what I should probably do more often, I kept my mouth shut. I told my Honors Physics class that they were going to prepare and present whiteboards of their video analysis of projectile motion from yesterday and define a general model for a ball thrown through the air. Furthermore, I wasn’t going to contribute to or guide the discussion. It was totally up to them.

I managed to keep my mouth shut and they managed to have the best whiteboarding discussion of the year. Their comments, questions, insights, and leadership were great. I took notes the whole time and will try to turn them into a blog post. More than once I cringed as it appeared the discussion was heading off the rails but each time someone stepped up with a great question or comment and brought the class back on track.

At the end of class, they gave me their model summary:

When I asked about motion graphs and mathematical models, they explained that there was no point to draw them. “We identified the balanced forces / constant velocity and unbalanced forces / constant acceleration models. Why draw the graphs again; we all know those models.” Nice.

  ##pmm ##whiteboarding ##paradigmlab  

Today, we started modeling projectile motion in Honors Physics. We filmed three examples of a ball being thrown and groups analyzed the videos using LoggerPro. I shared with students that they are ready to define this model without any assistance from me. Tomorrow, each group will present present their graphical and mathematical model and the class will define a general model for projectile model without any input from me!

  ##pmm ##paradigmlab  

Today in AP Physics B, we whiteboarded problems in preparation for tomorrow’s thermodynamics exam. One problem was from Giancoli (5th Edition), Chapter 15, problem 53 which reads: When 5.30e4 J of heat are added to a bass enclosed in a cylinder fitting with a light frictionless piston maintained at atmospheric pressure, the volume is observed to increase from 1.9 m³ to 4.1 m³. Calculate (a) the work done by the bass, and (b) the change in internal energy of the bass. (c) Graph this process on a PV diagram. Here’s their solution:

The answers matched the back of the book and make sense in terms of the calculations, but something didn’t sit right with me. I hoped one of the students would ask about it, but since no one did, I asked if we would expect the internal energy of the gas to increase or decrease based on the PV diagram. Since the pressure is constant and the volume is increasing, the internal energy must increase. However, based on the values supplied and the first law of thermodynamics, the change in internal energy is negative. After discussing, we decided that the values provided in the problem were just inconsistent and that the heat added to the gas should have been much larger. Are we right? Did I overlook something?

  ##whiteboarding ##mistakes  

As I captured before, 42 junior-high students have been working with their high school mentors to design, construct, and test underwater remote-operated vehicles (ROVs). Over the past several weeks, they have completed their designs, cut PVC pipe, glued together their frame, and mounted their motors. This week most groups were installing switches in their control box and wiring the switches and motors. They still have a lot of work to do, but we hope to see some ROVs in the water in a couple of weeks!

The decals were installed on the trailer for Huskie Robotics, FIRST Team 3061 earlier this week. Several of the students worked to replace the jack that we broke and install a new spare tire holder. We also now have a dolly with which to maneuver the trailer so we won’t break the jack again. I’m reminded how awesome the trailer looks every time I pull into the parking lot!

  ##local ##omgrobots  

We are now getting to the challenging problems where students apply the unbalanced-forces particle model to problems involving multiple objects and friction in unexpected ways. Here is one of my favorite problems:

The diagram below shows a large cube of mass 25 kg being accelerated across a friction- less level floor by a horizontal force, F. A small cube of mass 4.0 kg is in contact with the front surface of the cube. The coefficient of static friction between the cubes is 0.71. What is the minimum value of such that the small cube will not slide down the large cube’s side?

Here is one group’s whiteboard solution:

  ##ufpm ##whiteboarding  

I wanted to change the dynamics of students working on in-class practice programming activities. I had forgotten that also wanted to introduce pair programming at some point this semester. Now is a good time! I’m not an Extreme Programming zealot, but I am a proponent of Agile Software methodologies and believe pair programming can be quite valuable. We started watching this video to introduce the main concepts. I’m hoping that pair programming helps keep students more on tasks, the class move at a more similar pace, and struggling students better understand the concepts.

Here they are:

Problems involving someone in an elevator are some of my favorite problems to Whiteboard. It leads to a great discussion of the difference of the force of gravity and how heavy we “feel.” Riding in an elevator and feeling “heavy” or “light” is something that all students can relate to and then connect to the normal force of the elevator floor on the person. Often students have extraneous forces on their free-body diagram (usually the cable supporting the elevator). However, this group drew a great system schema that clearly showed the the cable was not interacting with the person and outside of the system.

  ##ufpm ##whiteboarding