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Teaching physics with Angry Birds: exploring the kinematics and dynamics of the game
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2013 Phys. Educ. 48 431
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Teaching physics with AngryBirds: exploring the kinematicsand dynamics of the gameM Rodrigues1,2 and P Simeao Carvalho2,3
1 Middle and High School Rodrigues de Freitas, Porto, Portugal2 IFIMUP, University of Porto, Rua do Campo Alegre s/n, 4169-007 Porto, Portugal3 Department of Physics and Astronomy, Faculty of Sciences, University of Porto,Rua do Campo Alegre s/n, 4169-007 Porto, Portugal
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AbstractIn this paper, we present classroom strategies for teaching kinematics atmiddle and high school levels, using Rovios famous game Angry Birds andthe video analyser software Tracker. We show how to take advantage of thisentertaining video game, by recording appropriate motions of birds thatstudents can explore by manipulating data, characterizing the red birdsmotion and fitting results to physical models. A dynamic approach is alsoaddressed to link gravitational force to projectile trajectories.
Students motivation is now an important goal inteaching physics, and the use of video games inclasses usually increases students attention. Infact, video games are appreciated by all kinds ofstudents. Angry Birds is a very popular game fromRovio, categorised as a physics game becausethe motion algorithms are based on the kinematicsof projectiles . We can use a video analyserto study the birds motion when launched by theplayer from the slingshot. To do so, we only needto record video clips from the game with a screenrecorder.
Kinematics analysis of the game can bean excellent teaching strategy at all levels ofeducation, either as an introduction to a subject,or as an application of kinematics and dynamicsconcepts, from a problem-solving perspective.
In this paper we show how to give a basickinematics treatment of the game with the help of
video analysis and modelling software (Tracker),and outline strategies for teaching kinematics inschools.
The gameAngry Birds is a game created initially for theApple iOS in 2009  and later adapted forcomputers and games consoles. Today, there areseveral thematic editions. It is a dynamic strategygame, based on the laws of physics for projectilemotion, where the objective is to destroy theegg-thieving pigs, housed in their buildings, bythrowing the angry birds against them with thehelp of a gigantic slingshot.
The screen recorderFraps is benchmarking freeware developed byBeepa  that indicates the number of framesper second displayed on the computer screen.
0031-9120/13/040431+07$33.00 c 2013 IOP Publishing Ltd P H Y S I C S E D U C A T I O N 48 (4) 431
M Rodrigues and P Simeao Carvalho
This program also allows image capture and videorecording of everything displayed on the screen.Here we use a version that captures video clips ofup to 30 s (which is enough for our purposes).
The video analyserTrackerToday, thanks to the evolution of video analysersin different areas of physics, such as biomechan-ics and biophysics, there is much free analysersoftware for didactic purposes. This is in generaleasy and intuitive to use, and provides excellenttools for teaching kinematics in schools.
We have used one of the best and mostpowerful freeware video analysersTracker. Thisopen source software is authored by Brown [4, 5]and was developed for the Open Source Physics(OSP) project . Tracker is also a data modellingtool because it incorporates the Data Tool module,created by the same author.
Tracker comes with a built-in manual, butwhenever students are not familiar with thissoftware we advise teachers to build simple,practical and appropriate guidelines for theactivity proposed.
To make measurements with Tracker (or anyother video analyser), it is necessary to know thereal dimensions of at least one object in the videoclip to allow conversion of the image dimensions,initially given in pixels, to real dimensions.Trackers Calibration Tape tool sets the value of100 units (pixels) for a predetermined length bydefault (figure 1). When a new value is introducedto the calibration tool the software divides thatvalue by the number of pixels of the length, fixingthe correspondence between one pixel and thestandard input unit; for example, converting thevideo pixel lengths into metres or centimetres.
When the video does not present any objectwith a known dimension, an arbitrary size canbe assigned to one of the objects shown in thevideo, or we can determine the real dimensionsof the game objects by making use of a simplesuppositionthe game takes place somewhere onEarth.
Preparation of educational materialElaboration of videos
The videos were recorded with Fraps, which wasset to record at 30 frames s1.
Figure 1. The calibration tape appears with a defaultvalue of 100, for a standard length of 100 pixels.Reproduced with permission from Rovio EntertainmentLtd.
It is desirable to launch the red bird in sucha way that it can hit the ground without collidingwith any obstacle, and also with the zoom set insuch a way that frame translational movementsand zooming of the image do not occur, keepingthe reference system of coordinates unchanged.Thus, visualization of the parabolic trajectory ofthe red bird is more evident (it is easily achievedat the first level of the game, as illustrated infigure 1). Note that for Fraps to capture 30 framesin each second effectively, it is necessary that thecomputer maths processor and video card are fastenough; otherwise repeated frames will appear inthe video.
Teaching strategiesTeaching kinematics at middle school level
Kinematics can be introduced at middle schoollevel by exploring Angry Birds.
To begin with, students may choose aconvenient position for the reference axes, definea standard length and unit (e.g. the teacher maysuggest that the height of the slingshot be 5 m),and track the birds position with time to visualizethe trajectory. Students should be encouragedto change the referential origin, and with thisprocedure observe what happens to the valuesdisplayed on the data table, in particular theposition and speed values. They may also beencouraged to change the values and dimensionsof the calibration tape, and draw conclusionsabout the importance of defining a standard unitof length.
The notion of stroboscopic images can beintroduced when interpreting the birds path, inwhich the spacing between successive positions
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Teaching physics with Angry Birds
has a direct relationship with time (for constanttime intervals), allowing first contact with theconcepts of speed and velocity.
These first video analysis procedures (cre-ating a referential, establishing a standard unitof length and tracing the path) represent aparticularly useful activity when students startstudying kinematics, because we can introduceand discuss the importance of fundamentalconcepts such as position, trajectory, movement,rest, etc in a practical and operational (hands on)way, making learning more effective. This kind ofactivity can be done: (1) at home as experimentalworkthe video and a guide can be provided onthe internet; or (2) collaboratively by students inthe classroom, if there are computers available forall of them (no more than two or three studentsper computer is strongly advised).
For a more advanced level, after tracingthe path teachers can introduce graphs ofposition versus time, speed versus time andacceleration versus time by analysing andinterpreting Trackers graphs. Indeed, these canbe seen simultaneously as the trajectory of thebirds motion is drawn in Trackers main window(up to three can be viewed at the same time),promoting debate concerning well-known studentmisconceptions about their interpretation ,namely the contradiction between the positiongraph and the trajectory of the body .
There is also space for more traditional(although very useful) strategies, such as askingstudents to build graphs of speed and accelerationfrom data tables, either on paper or with acomputer application (e.g. Excel). It is quiteimportant to explain how to calculate the speedand acceleration (see figure 2), based on thebirds positions; this will help students to betterunderstand these concepts from a mathematicaland a conceptual point of view. They will haveto apply algorithms to calculate the average speedand acceleration, and establish the limits forwhich it is physically acceptable to consider theseaverage values as the instantaneous speed andacceleration of objects.
Teachers can also introduce the conceptof composition of motions, exploring the twobasic types of motion discussed in the classroom(uniform rectilinear motion (urm) and uniformlyvaried rectilinear motion (uvrm)), and thecorresponding gra