Tag Archives: lesson

Physics Teaching 2.Uh-Oh

My first talk! Given at the STANYS 2011 Physics Breakfast on November 8th, 2011 in Rochester, New York


Links to resources mentioned in the talk:

A huge thank you to Gene Gordon for inviting me to speak at the breakfast. It was great to share my passions and meet my virtual colleagues face-to-face!

I’d love any feedback you have, positive and negative. Thanks!

Cross-class Collaboration Projects

Today’s post comes from Daryl Taylor, a high school physics and astronomy teacher in Connecticut. It was originally posted in response to this question on the NSTA Physics Listserv: “Has anyone had students collaborate with another class in a different locality for any class projects or assignments?”

I have, and love to, run collabs with various schools around the world just about any chance I can.

  1. We’ve recently run a parallax project (Astro-based) with a physics class in California; results weren’t great, but made the point.
  2. I run, based on a CIESE NJIT collab project, a “Circumference of Earth” collab any time I can get a school far away and at a very different latitude; results are always within a few %; unheard of accuracy in the Fizzix classroom.
  3. A few yrs ago, we ran a collab with a Forensics class in South Jersey. They were doing a “Who Done It” type of project and they (a teacher I used to work with) enlisted my Fizzix class help. They sent us images of blood spatter and foot and hand prints and the “crime” scene in general. My kids had to research and learn a little “blood spatter” physics, (including enlisting a guest expert from the local police dept!) and submitted their “FBI (Fizzix Blood Investigators) lab report” via PDF files and a Skype session. The Jersey Forensics class then went further and held a mock trial type thing with their Mock Trial Team and we watched as the audience and expert witnesses via Skype. Was great fun and kids (and I) learned the proverbial ton.
  4. Year-long project with another school to build a “self-sustaining human habitat in a locale considered non-habitable”. Kids decided to build a habitat under the Pacific Ocean (I thought the Moon or Mars, but NOOOOooo….) complete with alternate energy sources (including a ‘back-up’ nuclear plant…) and even a specific population hand-picked by the “planning committee”. Really cool. Did a lot of Distance Learning stuff and covered topics that absolutely amazed me.
  5. Also based on a CIESE project, The Boiling Point Project, I try to find a physics and/or chemistry class somewhere at a very high elevation, like Boulder or Denver or Mexico City, to run two collabs at once: boiling point of water and acceleration of gravity. If properly equipped and labs are run precisely, results on both are great. Email, text, and Skype are used to keep classes up to snuff with each other. In fact, each Lab group includes two of my kids and two of their kids so they HAVE to share and collab differently than a self-contained classroom situation.
  6. I’ve even just taken a basic high school lab like diffraction and ran a collab (Co-Lab, get it? I crack myself up….) with another school just to get twice the data and more worthy results. Also gets kids involved outside the “four walls”. It’s also quite cool to collab with a local or not-local college on regular class labs. They normally have fancy machines that go ‘ping’ while we don’t. Run the same lab and compare. Sometimes, the expensive machines that go ‘ping’ do no better than a meter stick and persistence. Sometimes the expensive machines that go ‘ping’ kick the meter stick’s butt.

Hope this helps. Anyone want to join some collabs this year?

Daryl L Taylor
Main website for teachers : DarylScience.com
Main website for students : DTFizzix.com
Teacher/Personal Blog: http://darylscience.blogspot.com/
Student Blog: http://dtfizzix.blogspot.com/

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:

Khan Academy: My Final Remarks

Many people aren’t getting the nuances of my recent Khan Academy arguments. I’ll make my final remarks and then put this thread to rest.

Khan Academy videos are nothing new. MIT OpenCourseWare has been around for TEN YEARS now. Walter Lewin’s awesome physics lectures have been available for most of those 10 years — despite the fact they are pseudoteaching, and his students emerged with no greater understanding of physics than those of professors before him.

And I didn’t have a problem with Khan Academy (as a collection of videos) until very recently.

For me, the problem is the way Khan Academy is being promoted. The way the media sees it as “revolutionizing education.” The way people with power and money view education as simply “sit-and-get.”

(c) tcoffey (via Flickr)

If your philosophy of education is sit-and-get, i.e., teaching is telling and learning is listening, then Khan Academy is way more efficient than classroom lecturing. Khan Academy does it better.

But TRUE progressive educators, TRUE education visionaries and revolutionaries don’t want to do these things better. We want to DO BETTER THINGS.

Ironically, everything that is wrong with Khan Academy has been addressed in two previous TED talks:

According to Dan, today’s math curriculum is teaching students to expect — and excel at — paint-by-numbers classwork, robbing kids of a skill more important than solving problems: formulating them. How does Khan Academy foster problem posing and creativity?

Rather than instructing students with Khan’s videos, we should be inspiring them to figure things out on their own and learn how to create their own knowledge by working together. For example, instead of relying on lectures and textbooks, the Modeling Instruction paradigm emphasizes active student construction of conceptual and mathematical models in an interactive learning community. Students are engaged with simple scenarios to learn to model the physical world. In comparison to traditional instruction, Modeling is extremely effective — under expert modeling instruction high school students average more than two standard deviations higher on a standard instrument for assessing conceptual understanding of physics.

Watch one Modeling class in action:

In the clip, the teacher says, “I don’t lecture at all. Instead, I create experiences for the students either in the lab or puzzles and problems for them to solve and it’s up to them to try to figure that out.” I’ve often wondered why this type of teaching hasn’t gotten more attention in the media. Maybe because the teacher is using simple things like whiteboards and bowling balls rather than shiny iPads and SmartBoards?

While Khan argues that his videos now eliminate “one-size-fits-all” education, his videos are exactly that. I tried finding Khan Academy videos for my students to use as references for studying, or to use as a tutorial when there’s a substitute teacher, but I haven’t found a good one. They either tackle problems that are too hard (college level) or they don’t use a lot of the multiple representations that are so fundamental to my teaching (kinematic graphs, interaction diagrams, energy pie graphs, momentum bar charts, color-coded circuit diagrams showing pressure and flow, etc.) Khan Academy videos do not align with proper Physics Education Research pedagogy.

I find it troublesome that the Khan Academy team is not spending time and energy on the pedagogy of teaching math and science, but rather on refining the gaming mechanics of Khan Academy in response to “good” and “bad” behavior of students working through the software exercises. The “gamification” of learning in Khan Academy has had disastrous consequences at the Los Altos school pilot.

There are some truly innovative learning technologies that have been
around for years. If Khan Academy wants to grow out of their infancy as electronic worksheet drills, I hope their team takes a look at these more transformative educational technologies, all of which have been researched and tested:

Khan Academy also promotes the “usefulness” of its dashboard for its exercise software. I find most of that information useless, like knowing how many times a student rewound the movie, how many times she paused it, or how long he spent on a module. Those times could be affected by distractions from family, self-imposed distractions like facebook and texting, etc.

Feedback I would find WAY MORE useful:

  • knowing how many times a student attempted the same problem
  • knowing the student’s answer history to each problem; i.e, what the student’s wrong answers were
  • knowing the type of mistake a student made when choosing a wrong answer; e.g., did he forget to square the distance, did she apply kinetic energy conservation instead of momentum conservation, did he disregard the fact that the forces where in opposite directions, did she confuse force of friction with coefficient of friction, did he assume constant velocity when in fact it was accelerating, etc.
  • software that anticipates and recognizes those common mistakes (like all great teachers do) and gives the students immediate, tailored feedback during the exercise

Finally, everyone is talking about using Khan Academy as a way to do more inquiry and more project-based learning. However, Bill Gates and Sal Khan are not showing any examples about what students and teachers are doing beyond Khan Academy. The news stories are not showing the open-ended problems the kids should be engaging with after mastering the basics — instead they show kids sitting in front of laptops working drills and watching videos. The focus is on the wrong things.

Khan Academy is just one tool in a teacher’s arsenal. (If it’s the only tool, that is a HUGE problem.) Khan Academy can be useful for some kids as vehicle (build skills) to help them get to better places (solving complex problems).

Now let’s please shift the focus (yours and mine) toward the destination.

Important Talks/Media about Khan Academy

More Blog Posts Critical of Khan Academy, from me and others

Khan Academy-Related Blogs

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.

References

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.

Increasing Engagement in Science

As part of a session on innovative practices in science at TeachMeet New Jersey 2011, I gave a presentation entitled “Tips, Tools, and Techniques for Increasing Engagement in Science”

I have posted that presentation, complete with speaker’s notes and plenty of links to further information, here: http://bit.ly/EngageSci

Any feedback you have would be greatly appreciated! (e.g., is there a bigger theme I am missing, etc.) Thanks! J3BC3J3HSY8J

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.)

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.

Also…

  • 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

Application

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*)

Notes

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!

Teaching Win or Teaching Fail? #1

What does good teaching look like?

If you asked me that question when I was a first-year teacher, I’d say the students would be sitting quietly and attentively. Ask me again today, and I’ll say the opposite.

I did plenty of classroom observations as a pre-service teacher, but I focused on the superficial details like student behavior and materials management. Once I began teaching, I was longing to go back and watch those same lessons again to pick up the pedagogy that had eluded me the first time.

And so, what I hope will become a series here, I present: Teaching Win or Teaching Fail?

How it works

I’ll post a clip of classroom teaching, an instructional video, or the like. In the comments section, our job is to hash out whether the clip is a teaching win or a teaching fail. I hope the wide range of opinions and perspectives will help us all become better teachers. And now, without further ado…

Teaching Win or Teaching Fail?

(Feed reader users should click through to see the video)

Everyone is welcome to participate, it doesn’t matter what subject area or grade level you teach. Hell, it doesn’t even matter IF you teach! The more viewpoints the better!

Teaching win or teaching fail? Please support your decision with explanations and evidence! And if you wish, let us know what you teach.  Let the wild rumpus start!

Win? Fail? PHYSICS!: An introduction

(Note: Feed reader users may need to click through to view embedded videos.)

A simple question

Real or fake?

Physics win or physics fail?

Inspired by Rhett Allain’s physics explanations at Dot Physics, Dan Meyer’s blog series “What Can You Do With This?”, and Dan’s TEDx plea for a math curriculum makeover, I have been collecting video clips that are prime for my physics students to analyze. The website is Win? Fail? Physics!

Videos are categorized by topic to help teachers locate videos for the concepts at hand. Several videos are listed under multiple topics. For example, the World Jump Day video above can be analyzed using Newton’s laws or conservation of momentum. The videos are presented without any further questions other than “Physics win or physics fail?” Kids watch the video and have an immediate visceral reaction. Now they just need evidence to support or refute their conviction.

What are they good for?

A WFP video can be the hook for the whole unit. The analysis will take several days as the students explore and experiment to develop an appropriate model. At the end of the unit, they return to the video to answer the question “Physics win or physics fail?” For example, my projectile motion unit starts and ends with the Kobe Bryant video (above), which I’ll outline in a future post.

A WFP video can also replace a textbook problem and the analysis can be done in a class period. Here’s a parallel end-of-chapter “problem” for the World Jump Day video:

How fast can you set the Earth recoiling? In particular, when you jump straight up as high as you can, what is the maximum recoil speed that you give to the Earth? Let your mass be 76.0 kg and your maximum jump height be 0.250 m. Model the Earth as a perfectly solid object whose mass is 5.98×1024 kg.

(a) Based on your maximum jump height, what must be your push-off speed?

(b) What is the recoil speed of Earth due to your jump?

(adapted from Physics for Scientists and Engineers, 6th edition by Serway and Jewitt)

The textbook gives students assumed values and guides students to the solution. Students lose out on important problem solving techniques as the textbook reduces a rich learning experience into an exercise in plug-and-chug.

Cognitive Weightlifting

The WFP video version strips the problem to its core: Win or Fail? Students do the cognitive weightlifting.  Working in groups, they must generate their own follow-up questions to solve and determine the knowns and unknowns. You can consider a good WFP to be a video version of a Context-Rich Problem.

Group A asks, “If every person on Earth jumped at the same time, how fast would the Earth move in the other direction?” while Group B asks, “How many people would have to jump in order to change the Earth’s orbital speed?” And in order to do solve their own questions, students will often have to make assumptions about certain values or conduct simple experiments to get those values.

Group A will need to know the mass of the Earth, the mass of a typical person, the number of people on the Earth, and a person’s typical push-off speed when jumping. A quick Google search yields the Earth’s mass and population. Group A assumes a typical person weighs 150 pounds and converts to mass in kilograms. However, they have no clue what a typical jump-off speed would be, so they decide to do an experiment to calculate it. One person jumps as high as they can, while group members measure the jump height, which they can then use to calculate the jump-off speed. Now Group A has what they need. They compute the recoil speed of Earth and compare it to Earth’s orbital speed via Google. Win or Fail?

Group B, on the other hand, looks up Earth’s orbital speed first and assumes that a 1% increase may be just enough to move the Earth slightly. They then do a similar analysis as Group A, but they compute the number of people needed to create that 1% increase and compare it to the Earth’s actual population. Win or Fail?

And, of course, there is Group C. They say gravity pulls the Earth and the people back together again anyway. Win or Fail?

Of course, the whole time I’m circulating around the room, helping groups and tossing questions back at the kids. Then we have a mini-conference where groups share their solutions on whiteboards and field questions from classmates. Finally, we reach consensus as a class. Win or Fail?

What it’s not

  • WFP is not  a demonstration.
  • WFP is not a talking-head documentary.
  • WFP is not a lecture or tutorial.

Want more?

Check out these sites for more possible WFP videos:

If you have suggestions for a WFP video to add to my online library, contact me with the URL. However, I do not have the time to take movie scenes from DVDs to upload to YouTube. Thanks!