Tag Archives: video

Khan Academy and the Effectiveness of Science Videos

This must-watch video is from our friend Derek Muller, physics educator and science video blogger.


Derek writes:

It is a common view that “if only someone could break this down and explain it clearly enough, more students would understand.” Khan Academy is a great example of this approach with its clear, concise videos on science. However it is debatable whether they really work. Research has shown that these types of videos may be positively received by students. They feel like they are learning and become more confident in their answers, but tests reveal they haven’t learned anything. [ed. note: textbook definition of pseudoteaching]

The apparent reason for the discrepancy is misconceptions. Students have existing ideas about scientific phenomena before viewing a video. If the video presents scientific concepts in a clear, well illustrated way, students believe they are learning but they do not engage with the media on a deep enough level to realize that what was is presented differs from their prior knowledge.

There is hope, however. Presenting students’ common misconceptions in a video alongside the scientific concepts has been shown to increase learning by increasing the amount of mental effort students expend while watching it.


My Ph.D. thesis, which includes the content from the publications below, can be downloaded here: Designing Effective Multimedia for Physics Education

2008 Muller, D. A., Sharma, M. D. and Reimann, P.,
Raising cognitive load with linear multimedia to promote conceptual changeScience Education92(2), 278-296

2008 Muller, D. A., Bewes, J., Sharma, M. D. and Reimann, P.
Saying the wrong thing: Improving learning with multimedia by including misconceptionsJournal of Computer Assisted Learning,24(2), 144-155

2008 Muller, D. A., Lee, K. J. and Sharma, M. D.
Coherence or interest: Which is most important in online multimedia learning?Australasian Journal of Educational Technology,24(2), 211-221

 2007 Muller, D. A., Sharma, M. D., Eklund, J. and Reimann, P.
Conceptual change through vicarious learning in an authentic physics settingInstructional Science35(6), 519-533

The implication of Derek’s research, both for online science videos and for in-the-classroom science lessons, are obvious. Derek discussed his PhD research in more detail in his previous post “What Puts the Pseudo in Pseudoteaching?” You can find more of Derek’s videos at Veritasium.com or on the Veritasium YouTube Channel. Follow him at @veritasium on Twitter.

What Puts the Pseudo in Pseudoteaching?

Today we have a guest post from Derek Muller, a physics educator who runs the science video blog Veritasium.  Derek is @veritasium on Twitter.

I have made some great pseudoteaching – but it was all in the name of research, let me assure you.

My interests in physics, education, and film converged in a doctoral dissertation at the University of Sydney starting in 2004. Since nearly all forms of education involve multimedia presentations in some form (e.g. a lecture with pictures, an illustrated text, an animation with narration, etc.), I proposed that, by studying this confined unit, we can learn some of the fundamental mechanics of teaching and learning which are at play in broader contexts. My central research question was:  how does one design effective multimedia to teach physics?

I made an eight-minute video on Newton’s First and Second Laws and it had all the hallmarks of outstanding pseudoteaching. Here’s a short excerpt from the video:

1. Looks like good teaching

  • The script was written as clearly and concisely as possible.
  • Ideas were demonstrated with concrete examples.
  • Animations were added to highlight the salient features of the examples.
  • Graphs for the motion were provided and explained with narration.
  • Research-based principles for multimedia design (developed by Richard Mayer and others) were adhered to.

2. Students feel like they are learning

  • Students were pre and post-tested plus a small group was interviewed.
  • Students reported higher confidence in the correctness of their answers on the post-test.
  • To describe the video, students used phrases like ‘simple’, ‘clear and concise’, ‘easy to understand,’ and ‘a good review’.

3. Very little learning takes place

  • For students with no high school physics, the average pre-test score was 6.0 out of 26.
  • The average post-test score, administered immediately after the video, was 6.3 (on the same questions).
  • Some students told me that they saw their (alternative) conceptions presented in the video (e.g. The force of her hand was greater than the force of friction so the book could slide with constant velocity).

Why I think lectures and videos so often amount to pseudoteaching

1. They are outside the zone of proximal development (ZPD)

  • Physics involves many interacting concepts. If students don’t have deep, well-defined, ideas about these concepts, the lecture will be well beyond their ZPD (and that is before we consider mathematical ability, misconceptions, etc.)

2. Misconceptions cause mis-perception

  • For example a misconception about acceleration – perhaps thinking of it as velocity – would mean a student is incapable of accurately perceiving what the lecturer is saying. Furthermore, if the lecturer is saying it in a clear, casual way, the student will think they understand it and that it corresponds to what they are thinking already.

3. Misconceptions cause proactive interference

  • Proactive interference is a construct from cognitive science. It is a term for when a previously learned idea/behavior interferes with a newly learned idea/behavior. I experienced this when I moved to Australia because here the light switches flick down for on and up for off.
  • Furthermore, this means that even if students have a ‘breakthrough’ they may revert to older ideas, days or weeks later. Just as I kept turning lights off, and turning on the windshield wipers (when trying to indicate) long after I knew what I really should be doing.

4. Lack of motivation and/or attention

  • Sometimes we all tune out. If the information does not pass our sensory buffer, it can have no effect on cognition.

5. No opportunity to ask questions

  • It is impossible to ask questions of a video and difficult to do in a lecture setting.

So what can be done to increase the effectiveness of multimedia presentations?

1. Make sure students are in the zone of proximal development

  • It is important that students have a strong understanding of the prerequisites.
  • It is also important that the educator knows the alternative conceptions prevalent in his/her audience. Having misconceptions puts students outside the ZPD even if their other prerequisites are strong.

2. Help the viewer correctly perceive the presentation by starting with the misconceptions

  • If the ideas that students are really thinking are presented first, they will perceive them correctly. This can then serve as a starting point for explaining how the scientific concept differs.

3.  Counter proactive interference by using previous conceptions as footholds

  • By tying into the student’s prior knowledge, the misconception acts as a conceptual peg on which the scientific knowledge is hung. According to studies on proactive interference (and science education research), the misconception is robust and likely to be recalled – so it is important that the scientific idea is closely tied to it.
  • The misconception should be discussed for its own merits – why is this idea so common? In what ways does it correctly reflect observations of the world? In what specific ways does it lead to inaccurate reasoning?

4. Make the presentation short and interesting. Use activities, questioning, reflection etc. around the presentation.

  • This should help keep attention and motivation.
  • Much of the learning would take place during the reflection activities.

The multimedia on Newton’s First and Second Laws that I outlined above I called the Exposition. I made two additional films, each of which included common misconceptions. One, called the Dialogue had the misconceptions presented as the genuine beliefs of one of the actors. Through discussion with the tutor character, these misconceptions were resolved. The other, called the Refutation, consisted of the same material as in the Exposition plus misconceptions stated and refuted. Here a short excerpt from the Dialogue:

After watching one of the misconception treatments, students’ confidence in the accuracy of their post-test answers improved about the same amount as after watching the Exposition. It seems watching any short instructional segment improves confidence by x. But in interviews they were more likely to say the video was ‘confusing’ or ‘hard to understand’. So how much did they learn? Scores on the post-test were significantly higher than for the Exposition treatment. In fact, students with no high school physics who watched the Dialogue nearly doubled their average score from 6 to 11 out of 26 (the Refutation was similar but not quite as impressive).

Even more interesting was how much mental effort students reported investing in watching the multimedia treatment. Students who watched the Exposition reported an average of about 5 out of 9 (‘neither low nor high mental effort’), whereas those who watched the Dialogue averaged 6 out of 9 (‘rather high mental effort’).  Depending on what is presented, students watch it in a different way (perhaps more actively), and that determines how much learning occurs.

How does this view help us understand teaching and learning more broadly?

For one thing, I think it shows that pseudoteaching is audience dependent.

In the discussion above I mainly used data from the Fundamentals stream – students with no high school physics background. Students in the Advanced stream (these are students who did well in high school physics) achieved the same gains across all multimedia treatments. Any ceiling effect would have been slight because their average post-test score was 85%.

Another pseudoteaching post mentioned how Feynman’s lectures became populated with graduate students and faculty. This is exactly the kind of audience for whom the lectures would not be pseudoteaching. These learners would:

  • Be in the Zone of Proximal Development.
  • Have few misconceptions (many fewer than undergraduates).
  • Have better formed schemas so proactive interference has less impact.
  • Be intrinsically motivated by physics and therefore very attentive to the presentation.

There is a remark often made at science education conferences, usually with a chuckle, “Can’t learn anything from these talks because you know we learn nothing from a lecture.” I hope everyone recognizes the problem with statements like these. We can learn from presentations. What and how much we learn comes down to the level of the presentation, our existing schemas and misconceptions, and our motivation and attention.

Full disclosure

I have the excellent fortune to rarely teach a class of more than 14 students. Most are very bright and keen and I have virtually no discipline issues. I know every student by name and one of my mottos is “never say anything a student could say for you.” My classes are much more a discussion than a lecture and I definitely feel like this is the best method for teaching and learning.

The point of this post is not to promote one-way presentations or video lectures. It is to raise the level of discussion about multimedia (and about teaching and learning more generally). I think the transmission/construction dichotomy is unproductive and misleading. It creates a very narrow view of education (like Animal Farm – “Four legs good, two legs bad,” “hands on good, hands off bad,” “doing good, listening bad,” “newfangled good, traditional bad,” etc.) Does constructivism really support hands-on, doing, not telling? I’m not sure it does. Constructivism says ‘learners construct there own understanding actively, by thinking,’ but it does not say how this can best be facilitated.  Listeners and viewers are not necessarily passive. I argue what is presented determines how the presentation is viewed which determines how much learning occurs.


My Ph.D., which includes the content from the publications below, can be downloaded here: Designing Effective Multimedia for Physics Education

2008 Muller, D. A., Sharma, M. D. and Reimann, P.,
Raising cognitive load with linear multimedia to promote conceptual changeScience Education92(2), 278-296

2008 Muller, D. A., Bewes, J., Sharma, M. D. and Reimann, P.
Saying the wrong thing: Improving learning with multimedia by including misconceptionsJournal of Computer Assisted Learning,24(2), 144-155

2008 Muller, D. A., Lee, K. J. and Sharma, M. D.
Coherence or interest: Which is most important in online multimedia learning?Australasian Journal of Educational Technology,24(2), 211-221

 2007 Muller, D. A., Sharma, M. D., Eklund, J. and Reimann, P.
Conceptual change through vicarious learning in an authentic physics settingInstructional Science35(6), 519-533


Derek’s Veritasium videos are crafted using the results from his research. Here’s a great example:

Be sure to check out the entire collection Veritasium.com and at the Veritasium YouTube channel. I would like to add that Derek’s results are important and should inform our face-to-face class discussions as well.

I Love JayCut

Action-Reaction isn’t turning into an edtech blog, I promise. However, my students and I have been using JayCut (a free, online video editor) to create video lab reports and video demonstrations from clips taken with our Flipcams.

One nice feature that has great potential is JayCut’s picture-in-picture. It started when I saw this awesome video taken from the point of view of the edge of a sword:

I thought, wouldn’t it be cool if there was a 3rd-person perspective synced up with the sword’s perspective? So I set out to create my own version using a Flipcam and a meter stick (not as cool as a sword, I know). I had a student use a second Flipcam to film me while I swung the “sword” around. We made sure we pressed the record buttons at the same time. Then I used JayCut to merge the two videos together. Here’s the result:

The picture-in-picture effect is really just a transition, but I made the transition last for the duration of both video clips, rather than having one clip transition to the other. In addition, you can see that JayCut allows you to add titles, still photos, and upload your own audio.

Do you remember my Visualizing Newton’s 3rd Law with Colliding Carts post a while back? Well, I just discovered that JayCut can also do variable playback speed. So today I merged the 4 videos from the post (plus 1 extra) and included slow-motion replays so you can see that both hoops are always equally compressed. Check it out:

(FYI: I snagged the royalty-free audio for both of my videos from Kevin MacLeod at incompetech.com.)

My students have also been experimenting with video lab reports. Here’s an example from an activity about shoes, friction, and tug-of-war:

I know this group’s experimental design can be improved, but I wanted you to see some actual student work. Doing a video was a choice — other groups wrote a more traditional report or presented to the class using whiteboards.

When your movie is complete in JayCut, you can publish the video to YouTube, publish it to JayCut’s own site, or download the file to your computer. You can also get an embed code to put the video into a webpage, blog, etc. without publishing to YouTube.  (I find the YouTube version to be higher quality, though.) When my students made video lab reports, they got the embed code and put their video on our private Edmodo class page.

JayCut will store all the clips, stills, audio, etc. you upload into your media library so you can use them over and over again. You can save your work and finish later. I don’t know of any file size limit or storage limit. I really can’t believe the site is free, and there’s also no advertising. You do have to sign up for an account, but I have not received any email or spam from JayCut.

That’s it. I just wanted to show everyone what JayCut can do!

(NOTE: Some media in this post may not display in feed readers and must be viewed on the website.)

15 Ideas for Using Digital Cameras in Science

1. Stop motion movies and flip books.

By taking multiple pictures, students would create a photo flip book or stop motion movie to demonstrate, as accurately as possible, a particular science concept or process. For some examples, see Dale Basler’s post Create stop-motion videos and learn physics. Another way to easily create stopmotion films is with SAM Animation software (more examples) and a webcam.   

2. Photographs of Lab Setups
Take photographs of lab setups so you’ll remember next year how you set it up. Embed the photos into lab handouts and add annotations and directions.

3. Science Photo Gallery

"Where Sand Meets Sea" by Kelsey Rose Weber

Students take pictures and explain the all of the science concepts present in their photo. Display student work in the classroom and around the school. It drives home the concept that science is everywhere! Exceptional work in physics could enter the American Association of Physics Teachers’ High School Physics Photo Contest

4. Photo/Video Analysis
This is different from #3 in that students would need to take a photo (student-created or teacher-created) and mathematically analyze it.  For example, students could photograph the water coming up out of the water fountain.  From the size and shape of the parabola, students could determine the initial speed of the water and the time it spends in the air. See also Speeding Problem and Kobe, Karplus, and Inquiry.

5. LED Motion Photos

by Amy Snyder, 2007

Students would take pictures with the shutter open a little longer than normal to capture motion.  Attaching LEDs to the subject would allow for “light traces” in the photograph.  See Sebastian Martin’s A Different Physics Class.

6. A super-accurate stopwatch
Many cameras have a video mode.  It could be used to film an event that takes such a short time (less than 2 seconds) that using a regular stopwatch would yield poor results because of human reaction time.  For example, students could measure the time it takes a ball to fall from the ceiling to the floor (which is less than 1 second) to determine the gravitational acceleration.  Recently, we were doing a lab where students studied how the spacing between dominoes affects how quickly the line of dominoes fall. Students were getting messy data because the falling times were so short.  If students had taken a video of the dominoes, they might have gotten more accurate falling times because they can look at it frame-by-frame at 30 fps.

7. End-of-year slide show for final exam review.

Make a  slide show from pictures of students doing lab work and participating in demonstrations.  At the end of the year,  use the slide show to review for the final.  Ask the students if they remembered what happened in the lab/demo and what concept it demonstrated.  Plus, it’s a great way to remember all the good times  during the year!

8. Video-based Labs
Sometimes, I only have one lab setup because the equipment is expensive or finicky. I used to run these as teacher-led demonstrations.  Now, I can take a video of the experiment in action and students get the data from the video and do a regular lab analysis.  Students must still recognize what data is important and know what to do with it, as with a traditional experiment.  For a great example, see: Coin on Rotating LP. (Be sure to click “Home” to see many more!)

9. Archiving Student Whiteboard Solutions

In groups of 3, my students often write-up problem solutions on large whiteboards and present them to the class.  Taking pictures of the whiteboards and archiving them on the class website would be perfect for student review and for students who were absent that day.  If that gets too much to handle (sheer volume), take a picture of an exceptionally well laid out solution and put it in the “Whiteboard Hall of Fame” or the “Whiteboard of the Week.”  Documenting exemplary work shows students the level of expectation we have for all of them! See more at Physics Whiteboards.

10. Mini Biography
Take pictures of students and attach to a mini biography students would submit at the beginning of the year.  Display bios around the room so you not only get to know your students, but they can learn more about each other! See an example from Dean Baird.

11. Picture Dictionary

"f=force" copyright AshleyJM

As a class create a picture dictionary where students take photos that illustrate a particular science concept (force, velocity, wave, force, charge, momentum, energy, equilibrium, etc). These pictures could be posted around the room, perhaps with equations added, as the year progresses. Much better to have student made posters than teacher ones! See the brilliant and clever Flickr photoset The ABCs of Physics.

12. Photo labels for equipment drawers
With all the equipment in science rooms, photo labels would be a great way to show the contents of the drawers to help students find things and to put them away. Plus, the photos would liven up the room!

13. Video lab reports

14. Safety Do’s and Don’ts
At the beginning of the year, all science teachers go over laboratory safety and have students and parents sign a safety contract. Creating a PowerPoint with photos of do’s and don’ts would be perfect! Plus, it could be pretty humorous. If the pictures were created by the class from the year before as a final project, the next year’s students would enjoy seeing their friends in the photos.

15. Demonstrations

In the above video, which cart felt more force? (i.e., which cart’s hoop flexed the most?) When debriefing after a demonstration, there are always a bunch of students who think they did/saw something that they really didn’t. They might be biased going in to the demo, and the demo doesn’t change that bias. By taking video of the demo, show them what REALLY happened. In the above video, students tend to focus on the speed of the carts, rather than the flexing of the hoops, even when you tell them to look at the hoops!

(NOTE: Some media in this post may not display in feed readers and must be viewed on the website.)

More High-Speed Camera Fun

My last post ended with a slow-motion video of falling rolls of paper towels. Here’s a few other videos we’ve taken with the high speed camera:

Ball Bounce Challenge
Students had to predict the drop height necessary in order for the ball to bounce back up to the height of the hoop. Each group was given a different ball. They could take any measurements they wanted with the ball — but the height of the hoop was not disclosed yet. When measurements were complete, the balls were sequestered and the hoop was put in place. Groups then performed more measurements and calculations. Upon determining the drop height, each group was given back their ball and had one chance to make a successful drop:

Reaction Time
Are you quick enough to catch the dollar bill without anticipating?

Falling Meterstick
A classic demonstration. Why do some of the dice stay on the meterstick and some do not? Can you predict how far out along the meterstick the dice will remain in contact with the stick?

Other collections of high-speed video clips

And one more video nicely illustrating Newton’s 1st Law:

Have you been using high-speed videos in the classroom? How?

(NOTE: Some media in this post may not display in feed readers and must be viewed on the website.)

Falling Rolls

Rotational motion is my favorite topic in AP Physics C: Mechanics. Here’s one reason why:
[taken from Why toast lands jelly-side down: zen and the art of physics demonstrations by Robert Ehrlich]

We did this as a final problem in our study of rotational energy. After working through a series of long equations from energy and kinematics, we discovered the final answer is surprisingly elegant:

UPDATE 12/27/2010: Thanks to Dan Fullerton’s class for catching our error. They analyzed the problem using a torque approach and came up with:

I double-checked our energy approach and now get the same answer as Dan. We must have made an algebra mistake somewhere. This is why I love physics — there is more than one way to solve a problem!

H is the drop height of the free-falling roll, h is the drop height of the unrolling roll, r and R are the inner and outer radii of the unrolling roll.

Using large rolls of paper towels, we tested our prediction. Here’s the result, captured in slow motion:

(Despite our mistake, the demo still works. From the video, it seems the students did not release the rolls simultaneously. Perhaps this compensated for our algebra error.)

They were just a tad excited when it worked. And yes, that class is all boys, much to my dismay.

What’s your favorite activity or demo for rotational motion?

Visualizing Newton’s 3rd Law with Colliding Carts

Compare the amount of flexing of the 2 metal hoops when the carts collide. What does this tell you about the size of the forces acting on the carts during the collision?

(For frame-by-frame viewing, click the “.mp4” link. When the video plays in your browser using Quicktime, pause the video before the collision and use the left-right arrow keys to advance the video one frame at a time. Compare the sizes of the hoops!)

FAST vs. SLOW (same mass)

Download now or watch on posterous

FastSlow.MP4 (1932 KB)

HEAVY vs. LIGHT (same speed)

Download now or watch on posterous

HeavyLight.MP4 (3646 KB)

HEAVY (moving) vs. LIGHT (at rest)

Download now or watch on posterous

HeavyIntoLight.MP4 (7620 KB)

HEAVY (at rest) vs. LIGHT (moving)

Download now or watch on posterous

LightIntoHeavy.MP4 (4048 KB)

Speeding Problem?

The Problem:
New playing fields are going to be built on the lot across the street from our school. Unfortunately, people will need to cross Route 121 (a 2-lane highway) to get to those fields.  Currently, the proposed pedestrian crossing is a crosswalk with a flashing yellow light. Is there a speeding problem on Route 121? Do you think the proposed crossing is adequate?

The Solution:
We are videoing the traffic in front of the school with Flip cams and analyzing the videos in LoggerPro. Luckily, the fence posts are 10 feet apart and are perfect for setting the scale in the analysis!

(Feed readers may need to click through to view embedded video.)

If the school had put a police officer or a “Your Speed Is…” sign in front of the school, people would slow down, and the data would not be representative of real traffic. We hope that by recording traffic from a distance, drivers will be more likely to maintain their true speed. We also hope to collect lots of data during different times of the day (different classes) to help in our analysis.

This simple activity serves as an introduction to video analysis, so students will have another data collection and analysis tool at their disposal for future labs of their own design.

Lesson Progression: Projectile Motion

(Feed reader users may need to click through to view embedded content.)

Stage 0

“So, as you can see by this free body diagram, gravity is the only force on the ball. Therefore, the ball will move with constant velocity forward while accelerating downward at 9.8 m/s2. Any questions? Great!”

Stage 1

Stage 2

Stage 3

Stage 4

Lesson: Kobe Bryant jumping over a pool of snakes. Real or Fake?

I’m no genius when it comes to this teaching thing. It took me 12 years to get from Stage 0 to Stage 4 for this lesson. And I still have plenty of lessons stuck in Stage 0 and Stage 1!

Stage 5


Kobe, Karplus, and Inquiry

Real or fake?

This video (taken from the Win/Fail Physics collection) is the beginning and the end of a mini learning cycle during my projectile motion unit. At the beginning of the unit, it’s the hook. At the end of the unit, it’s the assessment.

Creating a need to know

By the end of their first viewing, all of my students are yelling “That’s fake! No way!”

“Where’s your evidence?” I ask. “Convince me.”

And students come up with all kinds of weak excuses like “It just LOOKS fake!” or “No one could do that!”

“No,” I say. “Convince me with physics. Justify your claim with scientific evidence.”

(*crickets chirping*)

The kids now have a need to know. They want to know if the video is real or not, but they lack the tools and knowledge to support or refute their original claim. They are now willing to go down the rabbit hole with you.

Whenever possible, I frame my lessons around the Karplus learning cycle: Exploration, Invention, and Application. (It’s nothing special. In fact, most other learning cycles like 5E, 7E, and Modeling are strikingly similar.) Instead of relying on lectures and textbooks, I use the learning cycle so students can construct the conceptual and mathematical models themselves, all within an interactive learning community.  By this point in the year, my students have been through several cycles, including constant velocity motion, accelerated motion (including vertical free-fall motion), and balanced/unbalanced forces.

Exploration Phase

Our goal as a class is to develop a model for Kobe’s motion through the air. After some Socratic discussion, we conclude that Kobe’s motion, if real, could be similar to tossed ball. After all, both Kobe and the tossed ball only experience the downward pull of the Earth while in the air. Both Kobe and the ball move vertically and horizontally at the same time. However, as my Force Concept Inventory (FCI) results indicate, many of my students do not grasp the independence of horizontal and vertical motion. So I ask them to forget about Kobe for a minute, and we do two exploration activites:

  • Pirate Treasure Hunt: Each group gets 10 directions (e.g., “Walk 44 tiles north”). What they don’t know is that all the groups have the same 10 directions arranged in different orders. However, if they follow the steps in order, they will be walking through walls and out windows. Eventually, students realize they can combine all the north-south directions and all the east-west directions and simply walk X paces west and Y paces north. The follow-up class discussion about “Why did you do that?” really gets at the independence of horizontal and vertical motion.
  • Dropping/Shooting a Bullet: Student use ice cream cone shooter toys to answer the question: “When released at the same time, which hits the ground first: a horizontally shot bullet or a bullet dropped from the same height?” Predictions and justifications must be made. Some students see the connection right away. Others don’t, but the results make for great discussion afterwards.

Which hits the ground first?

Invention Phase

Now we know that horizontal and vertical motion are independent. But we need to create (invent) a more detailed model to describe the motion of a tossed ball. But how will we get the horizontal and vertical motion data in order to create the model? Through Socratic discussion, student decide that trying to mark the position of the ball in the air as it moves won’t work. Nor will using motion detectors.  Students decide to use our Flipcams to video themselves tossing the balls and then do a video analysis of the motion in Logger Pro. (Students had done video analysis earlier in the year.) But there are still more questions:

  • “Wouldn’t the motion depend on how fast the ball is tossed?”
  • “Wouldn’t the motion of a tall/skinny arc be different than a low/wide arc?”
  • “Wouldn’t the mass of the ball affect the motion?”

So, as a class, we decide to split up the data collection. One group will vary ball mass, another toss speed, and another arc shape. We’ll share the position vs. time and velocity vs. time graphs created and look for patterns in their shapes and in their equations. This is whole class inquiry — groups are doing different experiments and everyone’s data is needed. Everyone makes a contribution to our classroom scientific community.

Video analysis in Logger Pro (image credit: vernier.com)

After the data collection and analysis, students “whiteboard” their graphs and we have a “board meeting” where each group presents their results and then as a class we try to make connections among the groups and come to a consensus. At the end of the board meeting, the class has created a model for projectile motion:
In the horizontal direction…

  • All position vs. time graphs are straight lines. The slope of the line represents the horizontal speed, which remains constant during flight.  This is like our previous model of constant velocity motion.
  • All velocity vs. time graphs are flat lines. This means the horizontal acceleration is zero which matches up the horizontal position vs. time graph. Again, this is like our previous model of constant velocity motion.

In the vertical direction…

  • All position vs. time graphs are in the shape of upside-down parabolas, with the time-squared coefficient being about 5 m/s/s. This is like our previous model of accelerated motion in free-fall.
  • All velocity vs. time graphs have a slope of about -9.8 m/s/s. Again, this is like our previous model of accelerated motion in free-fall.


  • The mass of the ball doesn’t matter. Again, this is like our previous model of accelerated motion in free-fall.
  • Projectile motion is simply the combination of the constant velocity model (horizontal) and the acceleration motion model (vertical).

Presenting lab results


We are now ready to return to the Kobe Bryant video to apply the student’s newly created model for projectile motion. They decide to immediately feed the video into Logger Pro for analysis. Students are able to make a claim regarding the realness of the video, and justify that claim with evidence and reasoning. I ask them to accumulate as much evidence as possible in order to make a stronger case for their claim.

Groups that finish early are pushed further with more questions: Is Kobe’s horizontal speed reasonable? Is the vertical and horizonatal distances he leaps reasonable? How will you figure those out and make a claim to their possibility?

At the end, groups whiteboard their work again, groups present their results to the class, and we reach a class concensus. The debate here sometimes gets very heated.

And when they are all done, they still ask me, “Is it real?”

“You just figured it out yourselves!” I say. (*sigh*)


1. Robert Karplus workshop materials on reasoning and the learning cycle.:

2. If you don’t have Flipcams, a regular digital camera that shoots movies will do fine. And if you don’t have a digital camera, there are plenty of pre-fab projectile videos to use — have a look at Dolores Gende’s collection of physics videos for analysis.

3. Levels of Inquiry. This cycle has elements of both guided (Level 2) and open (Level 3) inquiry. I stay away from confirmation/verification (Level 0) at all costs. The coupled-inquiry cycle is an easy way to do more open inquiry in class.

4. For additional information about modeling, see the Modeling Workshop Project web site at Arizona State University. Here’s a great introductory article: Modeling Instruction: An Effective Model for Science Education

5. Rhett Allain’s wonderful analysis of the Kobe Bryant video was the inspiration for this learning cycle. Thanks, Rhett!