Day 140 – Wave Interference

Physics 11 – The main goal for today was for students to investigate wave interference and standing waves. However, I started the class off with some voting questions using the wave equation. As you can see above, this was not time wasted. Everyone clued in on the second round of voting and could explain their mistakes.

I’m using distributed practice for the wave equation. Students have done a bit of practice over 3 days. I still haven’t given them a worksheet on it. Maybe we’ll get to this next class. By the time they are quizzed on it, they will have practiced this equation/idea over 3 classes with each class spaced over 2-4 days apart.

Physics 11 – Today students explored waves with Slinkies.  They looked a properties such as amplitude, frequency and speed, as well as generating both transverse and longitudinal waves.  Students played with making waves will recording video on their phones. This allowed me to speak with each group individually and check their understanding of the wave properties.  All in all it was a pretty relaxed class but our goals for the lesson were achieved.

Day 134 – Finishing Momentum

Physics 11 – We did a bit more practice with conservation of momentum today, along with some Peer Instruction voting.  To help with one question, I fired up the good old air track, shown in the video above.  The air-track is good but it’s limited by the carts that I have for it and the lack of a good spring plunger.

One of today’s voting questions is below.  I keep forgetting that this is pretty tricky for physics 11.  On the one hand the correct answer is intuitive.  You load something up with more mass it will slow down.  Using the concept of total momentum being conserved is harder though because students want to know what happens to the momentum of the rain falling.

I briefly talk about how momentum is a vector and we have to consider that momentum that are perpendicular do not add together as a single number.  I then quickly try to change the topic as this is waaaay above where we’re at with the topic.

Day 130 – Conservation of Momentum

Physics 11 – We finally finished the video lab, after 2.5 days on it. Whew.  I’m afraid we don’t have much to show for it.  A few students had some insightful thoughts on what they observed but really it was too little for too much time spent. I blogged much more about it on my edblog.

One student was able to claim that it seems as though the momentum is transferring from one object to the other, which was a great thought. Another student reasoned that momentum should be conserved since Newton’s Third Law tells us that the forces are the same but in different direction, which means that whatever momentum one object gains, the other must lose.

Day 128 – Momentum Video Lab

Physics 11 – This is the lab I settled on for conservation of momentum.  Students will use three Direct Measurement videos (dart into cart; Hailey and Connor; Hailey, Connor and Christine) and three videos that they will record themselves of two carts on an air track (head on collision, collision in same direction, collision into a cart at rest).  I thought about giving them an Excel spreadsheet for entering in their data, but that would make the experiment very much a “black box”.  The amount of time this lab is taking is concerning though.

Day 126 – Oops.

Physics 11 – A couple of oops in the pictures above… First, the dreaded twisted slinky.  This is annoying but I sort of get why it can happen. The quiz however is much harder to understand.  What is it about my teaching which allows even one student to have such little understanding to make the mistakes shown above?  Sometimes teaching can be frustrating. It’s a constant puzzle to figure out what went wrong. I guess this is the intellectual challenge that keeps it interesting.

120 – Goal-less Introduction

Physics 11 – Today was our first day back after a 2 week spring break.  As a bit of a review and to try and treat physics as a coherent story, I had students consider a goal-less problem.  Their first task was to come up with some questions that they could answer. I hope to use a goal-less problem for a Performance Task but I’m really starting to feel some pressure in terms of curricular content.  For good or bad, it’s weighing on my mind.

This type of performance task is really what it’s all about though. If someone is a student of physics, they should be able to look at a situation and model it, without having someone prompt them through a series of questions.

Day 118 – Power Testing

Physics 11 – Today we did some testing on power.  Not assessment testing but seeing “who has the most power?”

I had volunteers run up two sets of stairs, and then we used time and Eg to find which student put out the most power.  As is always the case, the heaviest students have the most power for this short test.

I then told the kids about power curves in athletic performances. I thought a few of my higher achieving students would be interested in this, particularly because they also do high level sports, including nordic skiing.  The idea is that when you model power output from an athlete, you can plot their critical power. Critical power is the average power they can maintain for any particular time period.  In the chart above, Jamar can hold an average of 994 W for 4 s.  As the time interval gets longer, the power gets lower.  This can be modeled in different ways but it typically gets shown as being some type of second order inverse relation.  Endurance athletes, like nordic skiers, are usually most interested in shifting their curve up.  A shorter interval athlete is probably more interested in shifting the curve to the right.  In any event, none of the students were terribly interested in this. This probably helps explain why they don’t really care that much about modeling in general?  Oh, and it was the last day before spring break…