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14 October 2016

Mail Time: Why do we have to memorize facts in 9th grade conceptual physics?

In conceptual physics, I don't use a textbook.  Instead, the reference material for the class is contained in our "fact sheets."  These facts are handed out piecemeal to the class, about three to six sentences at a time as they're relevant to the current content.

You can see all the facts from the full conceptual course here; feel free to use these in your own class.

I ask students to learn the facts by heart.  We have occasional fill-in-the-blank quizzes in which they have to recall the important words in a fact; on homework, students are required to write these facts nearly word-for-word as the first step in responding to any physics problem (though they have access to notes for all homework). 

I got an email from Keri, who is using these fact sheets for the first time in her conceptual class.  She's encountered an unusual problem: her freshmen are complaining about having to memorize these facts.  How should she justify to students, parents, and administrators why a physics class requires remembering words?

Keri has three proposed responses: 

(1) Since she's giving students a formula sheet, they don't need to memorize formulas.  It's more important to memorize facts; and those facts won't be available during an exam.

(2) Paraphrasing the facts generally isn't enough, because it's too easy for a new student to miss something important in the paraphrase

(3) Facts should be instant-recall, not thought processing, so students can focus instead on the reasoning involved with each problem.  

Keri, that's a really interesting and unusual complaint. The vast majority of complaints that I get, and that other physics teachers report to me, are of the form "but I learned the facts and equations, I can spit them back, why aren't I getting an A?" Now, your students are saying, hey, don't make me memorize anything, THAT'S too hard, too! I suppose they're suggesting that we all just sit here and watch videos for a year? My cynical mind and experience as a baseball umpire draws the conclusion that people will kvetch about teachers regardless of what we do. Everyone thinks they can do a better job than we can, everyone's a critic. 

I've never been asked this particular question, but it deserves a good answer. You've given an excellent three-pronged argument. I'll elaborate on each prong.

 I love your answer #1. I'd add that memorizing facts is what allows students to deal with problems that aren't merely recitation of facts. How is anyone supposed to interpret a position-time graph if they can't remember that the steepness (or slope) determines the object's speed? 

In terms of paraphrasing, note that our daily quizzes don't say "Write fact #3 about velocity-time graphs word for word." They say, "on a velocity-time graph, the speed is determined by _____." If you can't tell me that's the vertical axis, you don't understand velocity-time graphs.  Now, I generally accept "y-axis" or something that's pretty danged close. My colleague Curtis, who taught me about this style of quiz, insists on word-for-word terminology pretty much because he wants the class using the same language as each other, and he wants quick recall not processing (which is your point #3 above). 

With ninth graders especially, we start by asking them to copy these facts by hand into a notebook. Then they can use their personally handwritten notes on some of the quizzes. For example, we'll give a quiz with notes the day after they get the facts. Then, after they've used the facts for a day or two, we give a later quiz without notes. There's so much repetition in our class -- via quizzes, writing on homework, writing on in-class exercises -- that student draw confidence and comfort from the rote knowledge of the facts that they develop.

And finally, remember that a lot of the whining you're hearing comes from a position of ignorance. You as a physicist know when a substitute word is truly a synonym, and when a substitute word changes the meaning. In the example above, "y-axis" and "vertical axis" have the same meaning, even to a first year student. But my students have written, "on a velocity-time graph, the speed is determined by the velocity." "Oh, come on, the vertical axis is velocity, so you know I meant that velocity is the vertical axis!" No, sorry. That doesn't make sense. I've chosen my words very carefully on those fact sheets so that learning the facts leads to understanding. 

Physics is already a difficult subject -- it becomes EASIER, not harder, when students learn the facts by rote. There's gotta be trust in you as the teacher, just as we trust the musician who tells her students to practice scales. You, not your students, not your parents, are the physics teaching expert. When your students have a physics degree and a job in your school teaching physics, then they can decide what is a correct fact of physics. That was your final point in the email: "because I said so!"

(Of course, feel free to hide behind me, too -- "Hey, it's not me, these were written by this AP physics reader who's published five books and a blog. Feel free to take your complaints to him." :-) )

Good luck, Keri, and to all using these fact sheets.  They work.  


  1. The link is for facts from trimester 1. Do you have a link for the other two trimesters? Thanks!

    1. Ryan, I don't right this instant, but if you'll email, I can send.


  2. I agree 100%, and would add one more reason: So they will understand what the teacher means by a certain word or phrase. Would a parent want their child to learn some vague paraphrase of a word they are learning in French class? Doubtful. This is the physics equivalent.

    And kudos to you for those two lovely lines about ammeters and voltmeters. The reason for those is so the kid won't fail a lab exam in college. Been there, seen the multimeter's fuse blown.