Flappy Bird Physics Is Real Life?

via Today’s iPhone

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.

Somewhere Mr Bourne is telling some kid that the physics on Flappy Bird is all wrong

— Ro (@ro_v_o) January 30, 2014

Flappy bird doesn't obey any laws of physics!!

— kubobubo (@VaclavekJakub) January 30, 2014

https://twitter.com/NurulAkiller/status/428892206754037760

https://twitter.com/MadsEltonNilsen/status/428794101899616256

https://twitter.com/ThatPuckBeaut/status/428781313433149440

https://twitter.com/garyscott_/status/428763347794665472

https://twitter.com/La_Tayy/status/428689724425785344

I wish physics even slightly applied in flappy bird

— Craig (@czegsmd) January 30, 2014

https://twitter.com/Bella_Bonita_/status/428680939326017536

https://twitter.com/maaddawwg/status/427833802140815361

Flappy bird defies physics

— Ꮳhrissy Ꭶchweninger⚓ (@pisssychrissy) January 27, 2014

Flappy bird physics is so unrealistic

— last name ever, first name anus (@Freakyydeacyy) January 27, 2014

Like on what planet does anything fall that fast?!!?!? Have you ever heard of physics flappy bird??

— Andrew (@andrew_campos96) January 28, 2014

Take everything you know about the laws of physics and throw them out the window: that's flappy bird

— Tim Morris (@timothycmorris_) January 28, 2014

https://twitter.com/184bader/status/428541838283116544

https://twitter.com/ImChase_WutIDK/status/428532979192049664

https://twitter.com/veeedoh/status/428419628600410112

 

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:

@fnoschese looks like those sorry folks need themselves some logger pro

— slowciopath (@sam_wolfson) January 30, 2014

 

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

@fnoschese you know what would make an awesome demo, dropping a ball and watching it fall with same accel as flappy bird. +

— John Burk (@occam98) January 31, 2014

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:

• PreLab: Energy of a Bouncing Ball 2013 (docx)
• Lab: Energy of a Bouncing Ball 2013 (docx)
• Ball Bounce Video (avi) — From Ball State’s Video Analysis: Real World Investigations for Physics and Mathematics

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?

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

Angry Birds in the Physics Classroom

I recently blogged that you can now play Angry Birds in your web browser. This opens up all sorts of video analysis possibilities for physics lessons and assessment. Students can easily make their own videos or you can pre-record your own. Videos can be recorded using Jing, Screencast-O-Matic, or Camtasia Studio. Analysis can be done in Logger Pro or Tracker.

Here are some possible investigations to carry out (shared by Michael Magnuson on the WNYPTA email list):

1. Make a reasonable estimate for the size of an angry bird, and determine the value of g in Angry Bird World. Why would the game designer want to have g be different than 9.8 m/s²?   Download Angry Birds video.

2. Does the blue angry bird conserve momentum during its split into three?  Download Red and Blue Birds video.

3. Does the white bird conserve momentum when it drops its bomb? Why would the game designer want the white bird to drop its bomb the way that it does?  Download White Bird video.

4. Describe in detail how the yellow bird changes velocity.  You will need to analyze more than one flight path to answer this question.  Download Yellow Birds video.

5. Shoot an angry bird so that it bounces off one of the blocks. Determine the coefficient of restitution and the mass of the angry bird.  Download Red Birds and Falling Block video.

You can download each video using the links above or get them all here.

Other posts with ideas about how to use Angry Birds in physics class:

• Rhett Allain’s analysis of The Physics of Angry Birds.
• John Burk’s post Introducing projectile motion using Angry Birds
• Peter Kupfer’s post Angry Birds and Physics

How have you used (or will use) Angry Birds in the classroom?

UPDATE 12-28-2011: Our class has been featured on CUNY-TV’s “Science and U!” Jump to 10:25 in the video below:

Red, Blue, and Yellow Angry Birds

Download the original video files:

• Red Birds and Falling Block
• Red and Blue Birds
• Yellow Birds

Angry Birds for Google Chrome

You can now play Angry Birds in Google Chrome! This makes getting footage for video analysis much easier. Here you go:

Download the video file for your own analysis. I used Camtasia Studio (free trial) to do the screen recording.

Enjoy!