# What is missing from a general physics course?

1. Dec 10, 2016

### robphy

2. Dec 10, 2016

### Hlud

I think we are both in error in our assumptions of the other. I am in no way arguing for the removal of mathematics from physics education (or even an introduction to physics course). Perhaps i will have to abandon the use of the term conceptual physics instead of asking the community to view it differently. I am arguing for a revamp of the problems we assign and the topics we cover in our general physics classes.

Consider the following two questions.
1) A block is at the top of a frictionless, flat ramp. When the block is released from rest, what energy changes does the block undergo as it travels to the bottom?

2) A 0.50 kg block is at the top of a frictionless, flat ramp, that is 1.0 m high. The block is released from rest. What is the block's speed at the bottom of the ramp?

Now, the first question will come under a lot of fire from physics teachers and professors alike. "By not applying a mathematical model, you are not doing physics!" I would wholeheartedly agree with this sentiment.

I do not want to defend the first question. But, why does the second question not come under much fire? Partly because we require more from the student than just to provide an answer. We want them to show their work and, as you have your students do, assess their answer. Now, i want to introduce a third question to the fold.

3) A block is released from rest at the top of a frictionless ramp that concaves inward. An identical block is released from rest from the top of a frictionless ramp that concaves outward. Which block will be moving faster upon reaching the bottom?

This question requires a mathematical response, like the first question. However, this question, unlike our second question, does not end at a result. It is the start of more questions. "Why do i receive the same result, despite two differently shaped ramps?" Question one lacks a result. It is hard to discuss results in physics if you are not generating any! Question two ends at the result. Question three takes me beyond the result.

Now, let's look at the topics covered in a general physics course. Generally, these courses are mechanics heavy. You start at the beginning of the text, and you go as far as you can before time runs out. In my old school, another reason for our general physics course being mechanics heavy was to prepare students for the now defunct AP Physics B curriculum. This frustrates me because all students are being treated as future physics majors.

The problem with this kind of course is twofold. We promise to open their eyes to a new way of seeing the world, but we cover far few phenomena (whether that phenomena is suitably explained classically or not). In my first year teaching, our school's general physics course spent over two months covering the motion of a ball, whether thrown or dropped in a vacuum (i.e. kinematics). We then revisited that same motion of a ball in terms of energy, for another few weeks. For a third of the school year, my class looked at the motion of a ball (that doesn't even roll!).

Secondly, mechanics is perhaps the most abstract part of the curriculum. You deal with definitions (force, momentum, and energy) that will serve useful in the rest of physics. In creating those definitions, modelling all sorts of objects as a point suffices. Well, it suffices for us, but not for the students. We are supposed to be wetting their feet in modelling, not drowning them.

3. Dec 10, 2016

### Hlud

From my first year teaching, i often expressed to my colleagues my frustrations about the state of physics education. "Well, this is how physics has always been taught" would be a common reply. The article raises serious doubts to the veracity of that claim. It is also comforting that their is such a prolonged history of improving physics education in high schools. What is not so comforting is the success of those reforms. Unfortunately, what is required to graduate with a degree in physics dictates the curricula of these general physics courses.

I remember you mentioning your desire to overhaul your curriculum. How successful would you consider yourself in this goal?

Because my school is a small K-12 school, the science teachers (all three of us) are working together to promote skills through the vehicle of concepts, as well. I'll have to look through that document to see if i can better articulate the skills we want our students to build.

4. Dec 10, 2016

### brainpushups

In terms of meeting my objectives of students developing a deeper understanding of the scientific process, the connection of scientific progress with cultural values, experiencing some sense of the creativity needed in science, and improving overall logical reasoning (ability to work within a set of assumptions – a theoretical framework) I think the redesigned curriculum is allowing students to meet these objectives very well. Students seem to agree for the most part and most like the way the course is structured (based on my first quarter course survey/evaluation).

The end of the first year was too rushed and I've decided to trim the content a bit which I was very uneasy about at first when planning this (the second) year so we'll see how I feel at the end of the year. My original plan was to end the course with Newton (which I did during the first year), but I ended up trying to cram too much other stuff in around it, partly because it was content I had always covered and thought was necessary: momentum, energy, and Newton's laws. This year I'm actually going to end with Galileo's theory projectile motion and reinstate a project that I had always done (except for last year) which does a good job connecting science, engineering, politics, and ethics – a project that actually seems to fit much better with this new structure. To end with Galileo I really had to convince myself that the content really doesn't matter as long as my objectives are being met. I wonder if this is the only introductory physics course that will not cover Newton...

I see this as my/my department's next step (there are also three of us). I want to better articulate not just the skill set and content set that students will leave my class with, but also what that looks like so students are aware when they've reached it. We've been talking about moving toward a proficiency based grading system, but I was never too impressed with models that I had seen until recently – standards always seemed so vague that if one were to do anything remotely scientific it seemed like students would be demonstrating knowledge of the standards. I think the set of 'transferrable skills' that I linked to in post 20 are also flawed in that way, as are probably all general standards. I've recently seen a few schools that have implemented proficiency based systems but they went as far as to include explicit statements about the level of rigor that is expected for meeting the standard.

One model of this that I liked was to have a set of four 'I can' statements, each corresponding to different levels of rigor within a given standard with the third level being a demonstration of 'proficiency' in the standard, level four exceeds the standard, and the first two levels are where students are as they approach the learning objective. I just started thinking about this on Tuesday and I have a (draft) of one example of what I mean.

On the set of transferrable skills is a category of 'self direction' and in that category is the indicator 'apply knowledge in familiar and new contexts.' A somewhat vague statement. So I thought of four levels of rigor that would make it clear to students what this looks like. When I wrote these I had in mind sort of 'standard' book work in physics - the indicator could certainly be interpreted differently.

1 - I can follow along with an example in a textbook or other resource
2 - I can apply my knowledge of a theory to explain and/or predict phenomena identical to specific examples that I have seen
3 - I can apply my knowledge of a theory to explain and/or predict new, but familiar, phenomena for which the approach to the explanation or prediction does not differ significantly from the approach of the texts or resources I have seen.
4 - I can apply my knowledge of a theory to explain and/or predict familiar or unfamiliar phenomena for which the approach is novel, or primarily designed by me.

I think that 3 is what most of us hope students can do.

5. Dec 12, 2016

### Hlud

I really like the self-awareness that you are working on. I know i want to get there in the future, but i need to get a better vision of my curriculum, first.

6. Dec 12, 2016

### Andy Resnick

Ah- now the thread is getting more interesting. Instead of talking about specific topics, we are now talking about overall 'learning objectives'. The AAPT article is good- thanks for the link. I also like the home-brewed version of Bloom's taxonomy.

Here's how I summarize the problem:

Intro physics courses are typically phrased as a liberal-arts version of the sciences. Students learn a little bit about a bunch of things, and overall the course is supposed to provide 'problem solving tools', 'ways of interpreting the world', etc. etc. This is no different than any other intro course, and so the unique voice of physics is overlooked. In opposition to those abstract goals, students are expected to learn specific skills: mathematical computation, measurement techniques, etc. This is no different than any vocational program, and so the unique voice of physics is again lost.

It should be possible to achieve balance between measurements of the real and analysis of the ideal.

In my experience, students struggle with identifying irrelevant parts of a problem that can be ignored and the essential parts of the problem. To be fair, some of this arises from poor problem statements. I advocate more use of estimation (Fermi problems) and approximation (what does 'frictionless' and 'flat' mean?) to bridge the two approaches. I also advocate that teachers spend more time on units and unit conversions. So, as an example, I would consider posing the following exam problems (note that I re-worded them from previous posting):

1) A block is at the top of a ramp. When the block is released, what energy changes occur as the block slides down the ramp?

2) A 20 pound block is at the top of a smooth ramp that is 10 feet high. The block is released from rest and allowed to slide down the ramp, and you are supposed to catch the block and set it down on the ground. Is this reasonable? (note- you may assume the ramp is frictionless, if you like).

These are open-ended questions that require interpretation by the student to answer. Students don't like these questions because there's not a (single) correct answer, and it's not clear how points are awarded.

A note for #2: for my (US) students, I have found that using imperial units paradoxically makes problems easier to comprehend but when gravity is involved, more difficult to solve. I spend a fair amount of time on mass vs. weight and why bathroom/produce scales can be misleading.

I'm very intrigued by this- please let us know how it went!