# Tag Archives: physics

## Flappy Bird Physics Is Real Life?

If you don’t already know, Flappy Bird is the hot new mobile game right now. The premise is simple: navigate the bird through the gaps between the green pipes. Tapping the screen gives a slight upward impulse to the bird. Stop tapping and the bird plummets to the ground. Timing and reflexes are the key to Flappy Bird success.

This game is HARD. It took me at least 10 minutes before I even made it past the first pair of pipes. And it’s not just me who finds the game difficult. Other folks have taken to Twitter to complain about Flappy Bird. They say the game is so difficult, that the physics must be WRONG.

So, is the physics unrealistic in Flappy Bird?

Sounds like a job for Logger Pro video analysis! I used my phone to take a video of Flappy Bird on my iPad. To keep the phone steady, I placed it on top of a ring stand with the iPad underneath.

(I’ve uploaded several of the videos here if you’d like to use them yourself or with students: Flappy Bird Videos.)

Then I imported the videos into Logger Pro and did a typical video analysis by tracking Flappy’s vertical position in the video. Sure enough, the upside-down parabolic curves indicate Flappy is undergoing downward acceleration.

But do the numerical values represent normal Earth-like gravity or insanely hard Jupiter gravity? In order to do this, we need to (1) set a scale in the video so that Logger Pro knows how big each pixel is in real life and (2) determine the slope of Flappy’s velocity-time graph while in free fall, which is equal to the gravitational acceleration.

The only thing we could realistically assume is the size of Flappy Bird. If we assume he’s as long as a robin (24 cm), then the slope of the velocity-time graph is 9.75 m/s/s, which is really close to Earth’s gravitational acceleration of 9.8 m/s/s. Flappy Bird is REAL LIFE.

So then why is everyone complaining that the game is unrealistic when, in fact, it is very realistic? I blame Angry Birds and lots of other video games. Repeating the same video analysis on Angry Birds and assuming the red bird is the size of a robin (24 cm), we get a gravitational acceleration of 2.5 m/s/s, which only 25% of Earth’s gravitational pull.

In order to make Angry Birds more fun to play, the programmers had to make the physics less realistic. People have gotten  used to it, and when a game like Flappy Bird comes along with realistic physics, people exclaim that it must be wrong. As one of my students notes:

UPDATE 31 Jan 2014:
Inspired by a tweet from John Burk,

we made a video showing Flappy Bird falling at the same rate as a basketball:

Here’s what I did: We determined from the analysis above that Flappy Bird is about 24 cm across. Conveniently, basketballs are also about 24 cm across. So I had my physics teacher colleague Dan Longhurst drop a basketball so I could video it with my iPad. Dan just needed to be the right distance away from the camera so that the size of the basketball on the iPad screen was the same size as Flappy Bird on the screen (1.5 cm). Next, I played the basketball drop video and Flappy Bird on side-by-side iPads and recorded that with my phone’s camera. Once I got the timing right, I uploaded the video to YouTube, trimmed it, made a slow motion version in YouTube editor, then stitched the real-time and slow motion videos together to create the final video you see above.

UPDATE 1 Feb 2014: While the gravitational acceleration in Flappy Bird is realistic, the impulse provided by the taps are NOT realistic. Here’s a velocity-time graph showing many taps. When a tap happens, the velocity graph rises upward:

As you can see, no matter what the pre-tap velocity (the velocity right before the graph rises up), the post-tap velocity is always the same (a bit more than 2 m/s on this scale). This means that the impulses are not constant. In real life, the taps should produce equal impulses, which means that we would see that the differences between pre- and post-tap velocities are constant.

TL;DR: Is the physics in Flappy Bird realistic? Yes AND no.
YES: The gravitational pull is constant, producing a constant downward acceleration of 9.8 m/s/s (if we scale the bird to the size of a robin).
NO: The impulse provided by each tap is variable in order to produce the same post-tap velocity. In real life, the impulse from each tap would be constant and produce the same change in velocity.

UPDATE 1 Feb 2014 (2): Fellow physics teacher Jared Keester did his own independent analysis and shares his findings in this video:

## Video Analysis of a Bouncing Ball

Nothing earth-shattering here. I just wanted to share the activity we worked on today, which was an introduction to quantitative energy conservation by doing a video analysis of a bouncing ball. (Up until now, we were only doing qualitative energy pie charts.) Here are the handouts and the video:

The graphs from the analysis are just beautiful:

Lots to talk about in those graphs!

Feel free to edit and reuse the handouts as you see fit. They’re not perfect, but I figure it’s better to share them than having them collect dust on my flash drive.

PS: I’ll sheepishly admit that I don’t do the whole suite of paradigm labs in the Modeling unit to mathematically derive the energy equations from experiments. But we do some simple qualitative demos/experiments to discover what variables would be in those energy equations. We start by talking about how the further a rubber band is stretched, the more energy it stores. Then we launch carts into a rubber band “bumper” (i.e., big rubber bands from Staples and two C-clamps) to qualitatively see the energy stored.

In doing so, we see that the cart’s kinetic energy depends on its speed and its mass. (Or is it weight? What would happen if we repeated the experiment on the moon?)

For gravitational energy, we can repeat the experiment, but have carts rolling down an incline. Or use the rubber band to launch the cart up the incline. I’ve also dropped balls into sand and looked at the depth to which they get buried. Either way, we see that gravitational energy depends on height and weight. (Or is it simply mass? What would happen on the moon?)

For elastic energy, we already know it depends on the distance the rubber band is stretched. Then, we can swap out the rubber band in the bumper with a stiffer/looser one to see the effects of the spring constant on energy stored.

Then, after we predict what the energy equations might look like, I just give them the actual energy equations, or have them look them up. (Gasp! See Schwartz’s A Time for Telling, aka Preparation for Future Learning.)

So, modelers, what am I missing by not doing the full-blown energy paradigm labs? How do you introduce the quantitative energy equations?

## Going Beyond the Physics Textbook

I have the honor of being invited by Discovery Education to attend their second “Beyond the Textbook” forum to be held this Wednesday and Thursday at their headquarters in Silver Spring, Maryland. The event is spearheaded by Steve Dembo and, in exchange for travel expenses, he gets to pick my brain about digital textbooks, resources, and curriculum. There will be 18 other outstanding educators as well, including my edu-heroes  Christopher DanielsonMichael DoyleKarl Fisch, and Tom Woodward.

In preparation for the event, I’m updating/remixing an old blog post I wrote called “My Vision for a Physics iBook” ….

~~~~~~

I keep thinking about what a physics iBook would look like. Not a book for consumption, as with a traditional text, but rather a book to enable exploration. So what would a student see when they first opened such a book?

It’s blank.

No content. No classical references like Feynman’s Lectures on Physics. No integration with Khan Academy’s video library.  Nothing.

Why?

Students should be learning to do science, not simply learning about science. They should be making observations, posing questions, conducting experiments, finding patterns, analyzing data, and sharing their conclusions.

In this sense, the iBook would function more like an electronic lab notebook. As with curricula like Modeling Instruction and ISLE, students would create the physics content from their own investigations and evidence, rather than deferring to authority.

Actually, the iBook wouldn’t be completely blank. While it would initially be empty of content, it would be chock-full of tools to help students collect and analyze experimental data. Software like Tracker for video analysis, VPython and GlowScript for computation and visualization, LoggerPro for graphing and electronic data collection, along with PhET simulations and Direct Measurement Physics Videos for conducting virtual experiments.

In the realm of traditional physics textbooks, only a few make it a priority to incorporate experiments into their storylines. Three that come to mind are:

The Manga Guide to Physics

Understanding Physics

FIGURE P-2  Electronic temperature sensors reveal that if equal amounts of hot and cold water mix the final temperature is the average of the initial temperatures.

and PSSC Physics.

Eugenia Etkina‘s upcoming College Physics text gets a step closer to my iBook vision. The text incorporates her work with video experiments in her ISLE and Physics Union Mathematics curriculula. In the text, there are QR codes which link to videos of the experiments to be analyzed.

For example, here’s a video of a momentum experiment, followed by the corresponding section of the text.

But, as you can see, the text does the analysis for the student. In my opinion, this would make a good reference only after the student has completed a similar activity on their own. Fortunately, her text also comes with a workbook that asks students to do this sort of scientific reasoning on their own:

Also taking the “experiments first” approach is Live Photo Physics Interactive Video Vignettes, a collaborative project by well-known physics education researchers Robert Teese, Priscilla Laws, and David Jackson. During a vignette, students are asked to make predictions and do video analysis on-the-fly. Here’s a preview:

Science is never done in isolation, however, so the iBook would come equipped with tools for sharing data, content, photos, videos, and resources among students and between teacher-student.

For me, going beyond the textbook means giving students a toolbox rather than an instruction manual.

What’s your vision for the future of textbooks?

You can follow along with us at the Beyond the Textbook forum this week by searching for the Twitter hashtag #BeyondTextbooks.

Bonus: 5 reasons why iPads won’t replace textbooks in science class.

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.

## My Vision for a Physics iBook

UPDATE 1/22/2012: Now with links and Apple’s iBook video!

Warning: This post is a brain dump of all thoughts and conversations I’ve been having about next generation textbooks since Apple’s iBook textbook announcement. Sorry this isn’t polished.

I keep thinking about what a physics iBook would look like. Not a book for consumption (like a traditional text) but rather a book to enable exploration. More like a text-journal-workbook-lab notebook combo, where students would create content from investigations (also pooling created content/data from classmates, etc) and also have reference text for afterwards in the same vein as the Minds-On-Physics text, the first edition of M&I, and the Physics by Inquiry texts.

Stuck on a problem? An intelligent tutor would be able to re-direct you back to a video or animation or even your own data from an exploration where you initially encountered the concept.

There would be these components:

It’d be like an electronic version of the PSSC/Modeling/ISLE /PUM curricula on steroids. And I see this more as the teacher having these tools to deploy to the students, rather than the students following a linear path through text and activities. The class actually builds the text together, and each year the text is different.

The capabilities and content for this iBook already exist. No one has put them together in one package yet. I think it could even be web/cloud-based and platform independent if done with the proper tools.

What am I missing? What’s your vision?

## 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