Tag Archives: problem solving

Projectile Motion Assessment Task

You are a game designer for Rovio Entertainment, the company that makes Angry Birds.  The human resources department wants your input. They are hiring several programmers to build the physics engine for Rovio’s newest game. Here are the demo videos from the top four applicants. Which applicant(s) would you recommend for hire?

Applicant A

Applicant B

Applicant C

Applicant D

Download the original video files for analysis in Logger Pro or Tracker.

These videos were not created by me. I found them online several years ago, but I can’t remember where. If anyone knows, please tell me so I can give the creator proper credit. Thanks!

My TEDxNYED Session: Learning Science by Doing Science

Many thanks to the TEDxNYED 2012 crew, especially True Life Media, Basil Kolani, Karen Blumberg, and Matthew Moran for an awesome event. Be sure to check out the rest of the TEDxNYED 2012 talks.

Learn more about Modeling Instruction in Science.

Physics of Angry Birds Lesson on CUNY-TV

Many thanks to Ernabel Demillo and the crew of Science and U!

You can read more about how we use Angry Birds in class here:
Angry Birds in the Physics Classroom

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!

Problem-solving Paralysis

Recently, I’ve been playing Refraction on my Android phone. The goal is to get the colored light beams from the triangles to the round targets by placing mirrors and prisms on the board to manipulate the light. It’s a neat little game that has both good and bad physics which would be great for analysis. But we can save that for another post.

Whoa. Where do I begin?

I’ve been thinking about what it’s like to solve an imposing puzzle:

  • I never “see” the full solution by simply looking at the puzzle.
  • I don’t wait to make my moves until I know the solution.
  • I take a few steps, and see where they lead.
  • Sometimes those steps don’t work out. So I backtrack and try again.
  • The forwards and backwards steps eventually add up to success.


I know my students take the same approach when solving puzzles, whether it’s video games, mobile games, crosswords, or sudoku. They dive right in and tinker. So why, when faced with a physics problem, do many students suddenly freeze-up if they can’t see the whole solution right from the outset? How do we show students it’s OK to dive right in, go down blind alleys, hit deadends, backtrack, and try again?

How do we eliminate problem-solving paralysis?

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:

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

Reassessment Experiment

CV.3 (A) I can solve problems involving average speed and average velocity.

That learning goal is the thorn in the sides of many of my students right now.

They took their midterm exam last week and many missed the question associated with that goal. The (A) denotes that it is a core goal.  Which means that, based on this grading scale:

their quarter grade cannot go above 69 until all core goals are met.

I handed the exams back in class yesterday.  Naturally, many students wanted to reassess on the spot. Since I have an archive of quizzes from previous years, it was easy for me to print out a bunch and let them have at it.

And most of them missed it again on the reassessment. No surprise there, really. Without any remediation, it was just another shot in the dark.

So as an experiment, I posted the following to our class’s Edmodo page today:

Does CV.3 have you Down? If so, do the following by Monday:

(1) Explain, in detail, the difference between average speed and average velocity. Simply writing the two equations won’t be sufficient.

(2) Describe in detail a situation where an object’s average speed and its average velocity have the same value.

(3) Describe in detail a situation where an object’s average speed and its average velocity have different values.

(4) Create your own physics problem involving average speed and average velocity that is NOT a simple “plug-and-chug” type problem. (For example, “A car travels 50 miles north in 2 hours. What is its average speed and velocity?” is NOT acceptable.) Write up both the problem and a complete solution. Feel free to use pictures, graphs (even video) as part of your problem. Check out this link for non-”plug-and-chug” problem types: http://tycphysics.org/TIPERs/tipersdefn.htm

(5) Cite all resources (classmates, parents, books, web pages, videos, etc.) you used. (It doesn’t have to be in proper MLA format. A simple list is fine.)

Submit you work HERE on Edmodo. You should upload a file (word, PDF, etc.). The work must be YOUR OWN. I can tell when “collaboration” is really copying.

I hope this provides both the necessary remediation and a unique opportunity to reassess beyond simple quiz questions. I am really excited to see what kind of problems they write. I have done student problem writing in the past, but was never pleased with the results. Perhaps by requiring them to create a TIPER problem, we can push past equation memorization and towards understanding.

This scenario has also raised a few more unanswered questions: Why do I have this goal in my course in the first place? Why do my students keep missing it even though all quizzes (and the midterm) are open notebook? And if so many students are missing it, is it really a “core” goal?

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?

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.