Khan vs. Karplus: Elevator Edition

Exhibit A: Sal Khan on elevators

Exhibit B: My students on elevators
Framed around the Karplus learning cycle (Exploration, Invention, and Application) my students construct the conceptual and mathematical models themselves.

1. Exploration Phase:

2. Invention Phase: 

  • Draw a motion diagram for the object attached to the scale when the scale is stationary, then being pulled up and then stops.
  • Draw a force diagram for the object attached to the scale when the scale is stationary, then being pulled up and then stops. Decide whether the force diagram is consistent with the motion diagram. How is the force diagram related ot the reading of the scale?
  • Use the force diagram and the idea under test to make a prediction of the relative readings of the scale.
  • Observe the experiment and reconcile the outcome with your prediction.

(Video and questions for this phase taken from Eugenia Etkina’s awesome site Physics Teaching Technology Resource which has many more video experiments.)

3. Application Phase:

Instead of showing our students a better lecture, let’s get them doing something better than lecture.

UPDATE: Welcome New York Times readers! Other recommended posts:

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20 responses to “Khan vs. Karplus: Elevator Edition

  1. It’s amazing. One approach I feel alseep in, the other got me very interested. Which one is actually learning? /wink.

  2. Nice. The best part is kids will learn big concepts without realizing it.

  3. I think it is so unfair that I did not get to have you as my physics teacher in high school. Not only does this make sense, it is so much more engaging — even for a resolutely non-scientific thinker like me!

    Keep fighting the good fight, Frank. Nothing succeeds like success.

    - Elizabeth (aka @cheesemonkeysf on Twitter)

  4. Question. How do we motivate the unmotivated? Kahn is only going to Get kids that care enough to get the grade. Kids that don’t care because the are too busy landing sweet skateboard moves are the issue. Motivated students will learn depth inspit of us. Kahn will never get those skate boarders inside the school. I can. I go to games, skate parks, call home and invest myself in the lives of my students. I make my class engaging and “trick” my kids into learning. Some still want the token, heck I want my paycheck. The joy I get is not payday but the times when the “aha moment” appears. That is what I work for. The system we currently have does not support learning for learning sake. We have to pass a test. I maintain that if we teach kids, the test will not be a problem. In my physics class I am at the end of the road. I am going to elementary teachers and encouraging them to teach depth. Creating anchors for me to latch on and continue to build is where I am headed. We wil see how it goes.

  5. Aww fer cryin’ out loud, we get it – you think you’re better than Khan Academy. You probably are, but the problem is that Khan Academy isn’t trying to replace you. All they’re trying to do is help out by filling a void. Instead of demonizing an encyclopedia of FREE resources, why not take advantage of them and use them as a tool to help increase student leaning?

    • I think that Frank’s campaign isn’t necessarily targeted at Khan Academy per se — it’s aimed more at the people who want to put it up on a pedestal as the be all and end all of education. I’m sure that if we comb through all the posts about Khan over the past few months, we can find some praise lurking in there. :-)

  6. Good work. I send my students in groups of 3-4 into our elevator with a bathroom scale (re-calibrated to Newtons to avoid some of the “weighty” issues many teenagers confront), as well as a mass on a spring scale and a mass on a triple-beam balance–this produces a nice discussion of the difference between mass and weight.
    I created a video of an elevator ride with a ball floating in water along side a mass on a spring. Before you see it, predict what will happen to the ball ( I also have data from an express elevator in SF going to the 55th floor restaurant ( — includes a Logger Pro file with the data).

  7. Elevators- a very poor example to pick, because even amongst people with strong backgrounds in physics and maths, fallacies will abound.

    Khan, for instance, has the poor person in the first elevator as weightless. A simple thought experiment shows the mistake here. If that person was built like a jellyfish, would Khan’s assertion of “no net force” have the Human looking like a jellyfish in the ocean, or on the beach? The concept of solids blocking solids is really only a ‘force’ in a much more specialised series of mathematical considerations- considerations that lead to the ‘impossibility’ of a physical explanation for inertia- for instance Feynman actually attempted to use time-travel to explain inertia: bet you don’t believe this.

    Anyway, the comparison above is just another stalking fallacy. Khan is doing a lesson in maths. The lower videos are doing a lesson in physics. I don’t know about American schools, but here in the UK we did stuff like the Khan video in our maths (notice the ‘s’ – mathematics is a ‘plural’ so the contraction must be as well) lessons, and stuff like the later videos in physics lessons.

    So, unless you are engaged in a moronic campaign of suggesting that physics videos are ‘better’ than maths videos, what exactly is this latest act of stalking supposed to be proving?

    • I would argue that elevators are a great example to choose, because even amongst people with strong backgrounds in physics and maths, fallacies will abound. Those make some of the best lessons and the best (and admittedly most challenging) learning experiences for kids.

  8. Hi. I was reading this, and was reminded of my childhood education. It reminded me of Kumon (my only relationship being reading about it later in my career). Here are my thoughts:

    1) Most people learning the traditional way, do nothing with what they learn, because they can’t apply it. They are computations without meaning. Those that do use it, are successful by their own merit.
    2) The failure of education can be traced to the way in which progress is made. Testing is very easy when there’s one unambiguous answer. GMAT, TOEFL, and primary, secondary and almost all schools are geared towards rating people. So people learn to compute. I learned the hard way. I took the GMAT once, and couldn’t compute because I had someone with “nervous tossing” in my ear (interrupting thought every 5 seconds for the entire test). I always tended looking at problems from different angles, never caring too much for speed initially. You get better with the GMAT if you test a hundred times for the typical question. You just automate it, and become “the very brightest”. I scored 40% percentile on math, and 99% percentile on verbal/logical reasoning (in spite of not being English native). It reinforced the feeling the testing is the root of the problem, not a consequence.
    3) This Kahn person brings the very same problems, but provides some relief. At least, kids can absorb these mechanical things faster. What if they allowed some kids to graduate at 8 years old? Then they would free them to actually start learning.
    4) Reminded me also about KUMON as I said. I read a lot, and most of the most successful students a) forgot most everything after a short while b) didn’t excel later on on their careers.
    5) I have seen many times people with low grades that become fabulously rich and successful. That’s because they didn’t bought “the testing game” so well (and so kept a different perspective on things), and the other half was just so bored that when freed, they excelled.
    6) Also reminded me of the phrase, “I can teach you, but I cannot understand for you”. “Understanding” is a too often underrated word. Knowing is an overstated word. The school system is about knowing, not about understanding. And it’s about knowing fast, based on a set of criteria so limited as to ensure that everyone that has been lobotomized with a billion exercises, can churn out an answer so fast, to end up believing they understand something.

    This is why I liked to make jokes during philosophy classes back when I was about 10 years old. Reading and summarizing Plato dialogs was the punishment to those folks making jokes during philosophy class (sane sarcasm that would set 1/one third of the class laughing out loud, those that got it). I kept joking, and got more “homework”. And I liked that punishment more than many other courses. Later on, I understood what that professor was doing.

    When you understand something, to put an example, and only then, a becomes a true knife. It becomes a tool to be used in a million different ways, contexts and situations, without even having to think about it. And you start to wonder about the types of knifes, materials, and then you can use them as screwdrivers, hammers (back), as electric conductors, as a saw (depending on knife), as a soldering tool, as a game (throwing, in a safe place), cutting, dicing, shaping, sharpening (another knife). As something to be laid out along with 100 other knifes to do an art piece, as a thing with certain hardness to be able to dent some types of things, but never others, as a perforator, etc, etc, etc. Yes, this is limited example, only when you really understand something, you can use it so many ways that it becomes so real that you can appear to be a magician to anyone with only knowledge of it.

    I wish schools different. I am worried about my 2 year old son becoming so bored, or uncreative, as to always need a “secure job”. You know, there’s one reason schools are like they are. People are trained to know, so they can become employed, and not employers. This is, ultimately, my belief. And the realization that schools like Kellogg or Harvard use GMAT and tools like that to screen out candidates, but their teaching is extremely tilted towards discussing cases, and expanding the understanding of things. To anyone reading this, my best advise is “play the game, but look beyond the game”

  9. I’m curious to hear your thoughts are about the book “Teach Like a Champion” and the accompanying dvd it has of what it considers exemplary teaching. Compared to Khan Academy, the hype surrounding the book has the potential to be more damaging to teachers who hope to teach by modeling rather than lecture because it is more likely to end up in the hands of those who train and evaluate teachers.

    • I agree with you. I hope that administrators look beyond the simple techniques in the book (some seem closer to boot camp than to teaching meant to instill a love a learning) and look at curriculum framework and classroom culture.

  10. Pingback: Insert your favorite “Wrath of Khan” joke blog title here « Greg DeKoenigsberg Speaks

  11. I think this attack on the Khan Academy is profoundly misguided.

    The mistake its author is making is this: he thinks that “modeling” is a magic bullet that can completely replace verbal explanations and repetitive drills. That is unrealistic.

    Drilling and explanation will always be necessary if education is to produce people who actually know their stuff and aren’t stumped by simple problems. Doing away with explanations and drills will only create an ignorant generation with huge gaps in their education. The “traditional” approach of step-by-step explanation and drilling has thousands of years’ worth of empirical support, and it produced the great philosophers and scientists of past generations, as well as many who are working today. The modern, constructivist approach has only idealism and half-cocked theory on its side.

    Khan is not presenting drills and explanations as a substitute for “modeling” and practical problem solving. Far from it. He’s saying that the flexibility and individuation afforded by moving lectures and drills online frees up classroom time for more practical and social group activity, including the sorts of things that constructivists want to see happening in the classroom.

    So you radical constructivist are setting up a false dichotomy — either drilling and explanation, or exploration and experiment. It’s not one or the other. They are complementary.

    • Modeling includes what you would call “drills” during the deployment phase of the model. Students employ their new models to solve problems in new labs, worksheets, practice problems, and eventually quizzes and tests of some sort.

      A previous poster is right–those of us who are blogging and speaking about Khan Academy as Frank is are doing so as opposition to those people who hold it up as the “end all be all” of education. It is a useful tool, but it is not a replacement for other educational methods, theory, or reform.

      There are places in Modeling where I think a Khan Academy method might work well, such as explaining and drilling on specific sub-topics (e.g. Motion Maps or graph analysis). But, as Frank’s comparison demonstrates, it isn’t a viable substitute for hands-on and minds-on model building for understanding physical concepts and mathematical relationships.

  12. Like other posters have said (and Frank, too, in my opinion) is that Khan Academy is a TOOL for teachers, parents, and students to use when needed. I don’t think any of us believes that any one tool is the end-all, be-all magic bullet for learning any more than we believe we can build a skyscraper with just a hammer. However, people such as Bill Gates and Sal Khan seem to be pushing one educational TOOL at the expense of other more effective and proven teaching METHODS and many people are jumping on the KA bandwagon simply because it’s supported by Gates.

    What strikes me is that we have two very extraordinary learners in Gates and Khan trying to revolutionize the delivery of educational content for a world of ordinary learners. I doubt Gates and Khan were typical learners or typical students. They both probably learned well from lectures and were bored silly in a typical classroom. They both probably sought knowledge from other sources. What we physics teachers actually have, however, is a mix of students. Some are bright, many have challenges, and most of them struggle to learn physics. Most, however, do not learn well by watching videos or lectures. Modeling is a teaching method that works for almost any learner and has decades of research supporting that claim.

    I’ve watched a few of the KA lessons on physics. Khan explains most of the math in typical physics teacher lecture style and, for the most part, does a good job of it. Since its a video, students can pause, replay, etc. when they need to and learn the algorithm well. There are no distractions from seeing the teacher or other students. There are also no opportunities for the student to ask questions or build understanding of a concept. It is strictly mathematics.

    Modeling Instruction is a teaching method that helps students develop understanding of a concept so that the mathematics makes sense because the learner understands the physics driving the given situation. Notice the order of the learning–conceptual understanding leads to mathematical reasoning. Modeling also addresses typical student misconceptions in a way that allows most students to replace incorrect ideas with the proper physics concept. KA appears to only be concerned with learning the mathematical procedure needed to solve a particular type of problem.

    In addition, Modeling develops evidence-based understanding that requires students to think through situations on their own. It is often difficult and frustrating to a student who is used to the teacher telling him what to do. Many studies have shown, though, that most people learn best (and most) when struggling to figure something out. When a toddler is trying to put the square block into the round hole is it best to take the block away and replace it with the round one? No! It’s better to let him struggle and develop the ideas of shape and size by doing. Its the same with learning physics. Students develop powerful problem-solving skills while struggling to figure things out. Please don’t misunderstand what I’m saying here. Students are given a team, experiences, and tools (motion maps, graphs, equations, free-body diagrams) to be successful. This is not haphazard “discovery” learning. Modeling Instruction is very thoroughly planned. The teacher knows where the students are going and gets them there. The outcome is different from lectures– students become solvers of problems rather than pluggers-in of equations and they understand where the mathematics fits into the big picture.

    My personal belief is that Modeling Instruction is a superior teaching METHOD and that KA is a teaching TOOL to be used as needed by parents, teachers, and students. I am basing this on 21 years of teaching experience, 11 of those spent teaching both high school and college physics classes.

  13. I think that, in the future, it is important to distinguish between different subjects when discussing The Most Effective Way to Teach.

    This is rather obvious, but everyone is talking past each other because when one person argues against one method, they have physics instruction in mind. Another argues in favor of it because he has reading instruction in mind. For me, personally, Khan Academy was an amazing additional resource for introductory statistics. Perhaps it’s much more difficult to model a statistics problem in the same way a creative teacher can model concepts from Newtonian physics.

    Please specify exactly what subject you’re referring to when you issue broad generalizations about The Best Way, and please consider that your opinion does not apply to other topics.

    Finally, let me just say that I really enjoy this website and thanks to Mr. Noschese for everything he’s done.

  14. Pingback: Notícias – Online Learning, Personalized | nerdenglish

  15. I saw the program on 60 minutes and I was just wonder if Khan Academy can help someone to become a better reader and to help past written test and get high test scores

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