Why is physics scarier than other math/science classes?

After some discussion with my student (geometry/chemistry) tonight, I think I have an answer to a question that plagued me for a while: why is physics scary?

It's scary because it's the first (and last) exposure to multi-step, multi-tool problem solving in math and science.
I had a high school student who found precalculus easy (or at least manageable, even that nasty stuff toward the end) but struggled mightily with physics problem solving. I couldn't figure it out for a while.

At first I thought it was that I found it easier to teach precalculus; the book is set up nicely, and I don't have to worry about abstract concepts (except insofar that I tried to tie it to useful stuff).

Then I thought maybe it had to do with the student having a weak science background. But by her own admission, she had both a weak math and science background.

It wasn't work ethic; this student worked a lot, both in class and outside. (I was dorm RA, so I knew studying was happening even outside of school hours.)

And I couldn't just chalk it up to "being Chinese", and the stereotype that Asian education consists of rote memorization and drills, leading to mathematical fluency but deficient creativity. (I secretly suspect this is an excuse perpetuated by Westerners to ignore the severe gap in educational readiness vis a vis other nations.) "Western" students in the same classes exhibited this pattern, too.

Eventually, it came down to this multi-step, multi-tool problem. Both she and I determined this independently.

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In the typical high school math class, you solve problems by using a single trick or tool.

In biology, you mostly memorize a bunch of concepts and vocabulary, which are evidently important skills in the first year of med school.

Chemistry presents perhaps the strongest challenge to this thesis. It is possible to generate a multi-step, multi-tool problem in chemistry. There's a reaction, and you have to figure out it's yield and reaction type. First, you might have to do some stoichiometry to balance the equation. Then, you might have to figure out Lewis structures to determine the number and type of bonds, and then calculate the binding dissociation energies. You can then figure out if the equation is endothermic or exothermic. Maybe you adjust the calculation using phase transitions. Then you can determine molar masses, and compare the expected mass to the measured mass, or some other contrived number that allows you to calculate the yield.

So maybe chemistry is the first opportunity. But my experience indicates that plenty of students muddle through chemistry and hit a solid brick wall when they take physics. So there's something different about it.

I think chemistry, in principle, can be taught with emphasis on using multi-step, multi-tool problems to solve chemistry problems. But in practice, it looks like that's not done. I don't have a good explanation why that is; I've never taught a chemistry course. (Those who tutor, teach or study chemistry: your input is definitely welcome.)

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In general, in the sciences, the problem statements are longer and more involved, making it less practical to have students do a number of problems on a single concept to hammer it in (as it's done in math). As much as we'd like to think otherwise, repetition and drills really do help cement a concept.

Maybe physics would be better if we could better segment subject material, and have more practice problems limited to one topic. This is different than how most textbooks are set up. Most of the better textbooks I've seen have, at the end of the chapter, problems grouped by topic, and prefaced with qualitative questions. It's not like a math book, where the section/chapter problems are divided into clusters in which you are asked to basically do the same thing over and over.

Physics, as a multi-step, multi-tool discipline, requires that all the tools work, and all the steps are clear. Maybe in other classes, even chemistry, a student can half-ass Lewis structures and still get an A. But it's just not possible to half-ass, say, linear momentum and be able to learn the rest. (Chemists: feel free to quibble and argue that the analogy ain't fair; I'll argue that even precious PV=nRT can be botched without irreparable damage to the rest of chemistry learning and the final grade.)

I'm not arguing that physics is better, or necessarily more complicated. But it is different.

Anyway, I think I'm going to revise how I teach physics. I basically need to generate drills, in addition to the problem-solving organizational methods that I'd ask them to use to convey their knowledge in a solution.