Spot the Physics. Dionysis Konstantinou Damjan Štrus

Transcription

1 Spo he Physics Dionysis Konsaninou Damjan Šrus

2 Spo he Physics 61 1 Summary In his uni we presen a few examples of how sudens can use smarphones o conduc physical video analysis of differen physical evens (movemens). I is possible o use he smarphone for he whole analysis, bu sudens can also combine he use of heir smarphones wih a freeware program named Tracker (or somehing similar). Keywords: Tracker, physics, video analysis Discipline: physics (linear and curved moions, oscillaions, collisions) Age level of sudens: years Android apps: VidAnalysis (will be released in December 214) ios apps: Adidas Snapsho, Video Physics from Vernier Furher compuer sofware: Tracker Circulaion of he ip of he second hand of a wach Circulaion of a car on a roundabou Elasic and inelasic collisions on he air slide You can find some examples of videos recorded by our sudens during heir projec work in school in he ibook. When he sudens are recording movemens, hey mus pay aenion o several very imporan facors. We will explain our ips using he example of an inclined hrow of a baskeball. nj njfig.1 Screensho from he video of an inclined hrow of a baskeball 2 Concepual inroducion The sudens prepare an experimen or observe an even (see examples below), record a video and impor he video ino an applicaion ha can make a physical analysis of he seleced phenomenon (a smarphone applicaion or Tracker). The aim is o have he sudens: Compare heir heoreical knowledge wih heir own daa, which hey have obained from a real-ime experimen or even, and/or Derive a physical law. This aciviy is very suiable for learning ouside he classroom (on an excursion, a rip, a summer camp ec.) in siuaions where he sudens have only heir smarphones wih hem. They can learn even while hey are riding along he highway on a bus insead of jus playing games. 3 Wha he sudens do The sudens firs have o decide wheher hey wan o record a new video, choose an exising video from heir smarphones or borrow a free video from Sample Videos (e-book, samples from Tracker or a similar program) and impor i ino heir smarphones. Below we offer a few examples of physical experimens or evens ha sudens can record wih heir smarphones: An inclined hrow of a baskeball A horizonal hrow of a baskeball A free fall and verical hrow of a baskeball Acceleraion of a cyclis on a horizonal surface (using differen gears) Downhill free acceleraion of a cyclis (or a ennis ball) Harmonic and damped oscillaions of a spring During he recording, he sudens mus hold heir smarphones seady. They should no move he camera, because he analysis assumes he camera is in a fixed posiion. They also have o keep he plane of moion parallel o he plane of he camera lens. The objec in moion should remain approximaely in a plane perpendicular o he viewing direcion. The video mus be aken from he smalles possible disance, bu i is necessary o record he enire moion. In our example, his means ha he baskeball should no disappear from he video a he op of he parabola. The sudens need o measure a real dimension of he moving objec in order o scale he video. In our example we measured he diameer of he baskeball. During he recording process, he sudens should consider he lighing condiions in order o have as clear a video as possible. Afer recording he video and imporing i ino he applicaion, he sudens should make a physical analysis of he seleced phenomenon. To conduc he video analysis, he sudens can use one of he apps menioned above, i.e. Tracker or a similar program. You can find complee insrucions for using Tracker in he isage 1 brochure, which is available a

3 62 Spo he Physics The main par of he analysis is o obain graphs such as x(), y(), y(x), v x (), v y (), v(), E kin (), E po (y) ec. The sudens will use hese graphs o derive furher experimenal daa, which hey can compare wih a heory and use for furher calculaions. Below are a few resuls (graphs) and ips concerning he seleced example (an inclined hrow of a baskeball). FIG.2 Graph x() of he inclined hrow x Furher asks for sudens: 1. Wrie a mahemaical equaion for he parabola. Wrie a physical equaion for he pah of he ball in an inclined hrow. Think abou wha informaion you can ge from he parameers of he parabola. FIG. 3 shows he acual pah of he ball. The curve is called a parabola, and he smarphone applicaion or Tracker allows you o fi he pah and ge he parabola s parameers. 2. The sudens should plo four addiional graphs based on Graphs 1 and 2 before hey look a he soluion: FIG.4 Graph y(x) of he inclined hrow ball (, y) From FIG. 2 you can see ha v x is consan; on he x-axis he uni is meres, on he -axis he uni is seconds. Below his graph is he equaion of he fi (x=a +b), and he program gives us he value for he velociy of he ball in he horizonal direcion (parameer a): v x = 4.3 m/s. Furher asks for sudens: Conver his value ino km/h and mph. Choose wo poins from he line, calculae he slope and compare i wih he v x value. FIG.3 Graph y() of he inclined hrow 1. y x Graphs v x () and v y () Graphs a x () and a y () FIG.5 Graph showing he change in he velociy in he verical dimension during he hrow y ball (, y) Vy On he y-axis he uni is meres, on he -axis he uni is seconds. The slope of he angen of he parabola shows he velociy of our ball. The sign of he slope changes ha is because he direcion of he ball in he verical direcion changes. The ball reaches he highes poin a he verex, where he slope of he angen is zero FIG. 5 shows he change in he velociy in he verical dimension during he hrow; on he v y -axis he uni is meres per second, on he -axis he uni is seconds.

4 Spo he Physics Choose wo poins from he line and calculae he slope of he line. Do no forge o calculae wih unis. Below his graph is he fi equaion (v y =a +b). Compare he calculaed slope wih he parameer a. You will ge he acceleraion of his moion. In his case a = 1.7 m/s 2 (i should be g). Read off he inercep of he line on he verical axis (v y ). You will ge he iniial velociy of he ball in he verical direcion (parameer b = v y = 6.4 m/s). Use he fi equaion for calculaing he ime he ball akes o rise v y =a +b. In his case =.6 s. Using he previous daa, calculae he highes poin ha he ball reaches during his inclined hrow. In his case, i is h max = 1.9 m. You can also check your calculaion in FIG. 3. Think abou wha informaion you will ge if you calculae he area beween he line of his graph and he -axis. Then calculae he size of his area (do no forge he unis). 5 Conclusion The sudens can es a physical heory wih he help of heir own experimens and real-life evens. They use heir own smarphones as measuring devices, and o conduc he analysis hey once again use heir smarphones or compuers and jus click on he mouse boh devices are sudens favourie ools/oys nowadays. If he resuls of heir experimen fi he heory, hey receive confirmaion; if he resuls do no fi, hey can hink abou he reasons for ha (i may be air resisance, or hey may have o hink abou doing he same experimen under differen condiions). By selecing and analysing an appropriae experimen, he sudens can poenially formulae a physical law. 6 Personal experience Sudens learn or review how o record useful videos, learn o use video analysis ools and hink abou he reasons why hey may end up wih differences beween heory and pracice. And finally, a few words abou VidAnalysis, a mobile applicaion ha runs on he Android operaing sysem and was developed by Richard Sadek in 214 (release in December 214). The use of his app a an early sage enables he sudens o learn abou he basics of he physical analysis of dynamic phenomena. The operaion of he app is quie similar o he previously described ools. A he beginning i is necessary o record a physical phenomenon, impor he video ino he app and deermine he ypical lengh of he phenomenon in he video. The main challenge, once again, is o deermine he posiion of a moving body as accuraely as possible. This is a major problem, because i is very difficul o ap precisely wih your finger on he moving body on he smarphone s screen. Once his is done, he applicaion immediaely presens a graphical analysis of x(), y() and y(x). 4 Cooperaion opion We can organise cooperaion beween differen schools. The sudens a he firs school prepare an experimen, record a video and send i o he second school s sudens, who analyse i in Tracker and wrie a repor (and vice versa). During he cooperaion hey can mee hrough Skype, Viber or any oher ool ha is appropriae for a video conference and alk abou heir experiences.

5 Imprin aken from isage 2 Smarphones in Science Teaching available in English and German published by Science on Sage Deuschland e.v. Possraße 4/ Berlin Germany Revision and Translaion TransForm Gesellschaf für Sprachen- und Mediendiense mbh Credis The auhors have checked all aspecs of copyrigh for he images and exs used in his publicaion o he bes of heir knowledge. Design WEBERSUPIRAN.berlin Illusraion acke aelier für kommunikaion Please order from info@science-on-sage.de Science on Sage The European Nework for Science Teachers is a nework of and for science, echnology, engineering and mahemaics (STEM) eachers of all school levels. provides a European plaform for he exchange of eaching ideas. highlighs he imporance of science and echnology in schools and among he public. The main supporer of Science on Sage is he Federaion of German Employers' Associaions in he Meal and Elecrical Engineering Indusries (GESAMTMETALL) wih is iniiaive hink ING. Creaive-Commons-License: Aribuion Non-Commercial Share Alike Firs ediion published in 214 Science on Sage Deuschland e.v. Join in - find your counry on Subscribe for our newsleer: Main supporer