Presentation on theme: "Physics course exercises"— Presentation transcript:
1 Physics course exercises Liceo Scientifico Isaac Newton - RomaPotential energy andmechanical energy conservationin accordo con il Ministero dell’Istruzione, Università, Ricercae sulla base dellePolitiche Linguistiche della Commissione Europeapercorso formativo a carattere tematico-linguistico-didattico-metodologicoscuola secondaria di secondo gradoa cura di Serenella Iacino
2 Indice modulo clil Strategies – Before Prerequisites Linking to Previous Knowledge and PredictingGlossary Italian / EnglishStrategies – DuringVideoKeywords riferite al video attraverso esercitazioni mirateConceptual MapStrategies – AfterExercises:- Multiple Choice- Matching- True / False- Cloze or Completion- Flow Chart- Think and DiscussSummary and Summary QuestionsWeb References di approfondimento come input interattivi per test orali escritti e per esercitazioni basate sul Problem SolvingAnswer sheets
3 Strategies Before Prerequisities 1Strategies BeforePrerequisitiesPhysicsMathsthe prerequisites arethe prerequisites arethe free-body diagramnewton’s second lawconcept of mechanical workwork done by gravitywork done by elastic forcekinetic energywork-energy theoremdot product of two vectorfunzioni goniometrichefirst theorem for right-angletriangles of trigonometryEnergy conservation
4 Linking to Previous Knowledge and Predicting Strategies BeforeLinking to Previous Knowledge and PredictingDo you know the dot product of two vectors?Are you able to draw the free-body diagram?How do you define the work done by a force on an object?What is the work done by gravity and by elastic force?How do you define kinetic energy?Do you know the work–energy theorem?2
6 Strategies Before Glossary Italian / English forza di gravità - gravityforza elastica – elastic forceforza non conservativa – non conservative forceforza normale – normallunghezza – lengthmolla allungata – stretched springmolla compressa – compressed springmoto – motionperpendicolare – perpendicularspostamento – displacementteorema dell’energia cinetica – work-energy theoremunità di misura – unit of measurevelocità – velocityverticale – verticalvettore - vector
7 Strategies During Keywords 4Strategies DuringKeywordsCircle the odd one outVelocity, gravitational potential energy, conservative, friction, closed route, kinetic energy, height, length, breadth, change of mechanical energy, normal force, electric potential energy, elastic potential energy, energy conservation, compressed spring, gravity, sound energy, displacement, thermal energy.
8 Complete the Conceptual Map 5Strategies DuringComplete the Conceptual Mapmechanical energygravitationalpotentialenergyelasticpotentialenergywork done by conservativeforces and nonconservative forceswork done byconservative forcesvariation ofmechanical energyenergy conservationkinetic energypotential energy
9 Strategies After 6 Multiple Choice A helicopter drops a case of humanitarian aid from a height of 25 m.What is the velocity of the case when it reaches theground?5.0 m / s8.0 m / s12 m / s22 m / s
10 Strategies After Multiple Choice 0.39 m 0.41 m 1 m A bar of soap falls onto a shower tray with an initial velocity v = 1 m/s ; if it reaches the tray at 3 m/s, what is the height from which it falls?None ofthese0.39 m0.41 m1 m
11 Strategies After Multiple Choice 2.66 10 J 2.27 10 J 3.91 10 J An airplane of mass m = 1250 Kg flies with a constant velocity v = 25.0 m/s at a height of 185 m.What is its total mechanical energy?JJJJ65
12 Strategies After Multiple Choice 4 v 2 v v / 2 8 v In Sherwood forest, Robin Hood shoots an arrow vertically upward with a velocity v.In the point of maximum height, the arrow reaches a potential energy U.If its potential energy is 4U, what is its initial velocity?4 v2 vv / 28 v
13 Strategies After 7 Matching Match the graphs with the kinetic energy in function of the velocity v, the elastic potential energy in function of the stretching x and the gravitational potential energy in function of the height h.123UhKvUx
14 Strategies After Matching -47 J -104 J -66 J Match the graphs with the correct values of the work done by friction force on a box of mass m=3.7 kg, that moves on a floor from one point A to another point B, if the coefficient of friction is 0.26.4.0 m1.0 m4.0 m1.0 m1.0 m1.0 mBB1B232.0 mA3.0 mAA2.0 m1.0 m3.0 m-47 J-104 J-66 J
15 Strategies After True/False T F T F 8Strategies AfterTrue/FalseIgnoring the resistance of the air, if a bullet is fired vertically upward, at the point of maximum height, its potential energy is greatest.TFA conservative force always does work equal to zero.TF
16 Strategies After True/False T F T F The work done by friction through a closed route is zero.TFThe work done by a non conservative force is equal to the change of mechanical energy.TF
17 Strategies After True/False T F T F If the forces are conservative or non conservative, the change of kinetic energy is equal to the work done by them.TFElastic potential energy is the work done by elastic force to return the spring to its initial positionTF
18 Strategies After 9 Completion Exercise Complete these sentences: Gravitational potential energy is the work and depends only onElastic potential energy is the energy of aA force is called conservative if
19 Strategies After Completion Exercise Complete these sentences: Friction is a non in fact friction always opposes and does work that is transformedMechanical energy is conserved only in the system in which are involved.The work done by a non conservative force is equal to
20 Strategies After 10 Flow Chart startComplete the flow chart in order to determine the final velocity of a wagon of the Roller Coaster that goes down, without friction, from an initial position A, having height h to the ground, to a final position B, having height h to the ground.ABthen the initial potential energyso apply the Energy Conservationenddetermine the initial kinetic energyand also the final mechanical energy
21 Strategies After 11 Think and Discuss The following activity can be performed in a written or oral form. The teacher will choose the modality, depending on the ability (writing or speaking ) that needs to be developed.The contexts in which the task will be presented to the students are:A student is writing an article about energy and chemical transformationsA student is preparing for an interview on a local TV about the transformation of the gravitational potential energy into heat.The student should:Write an article or prepare an interview;Prepare the article or the debate, outlining the main points of the argument, on the basis of what has been studied;If the written activity is the modality chosen by the teacher, the student should provide a written article, indicating the target of readers to whom the article is addressed and the type of magazine / newspaper / school magazine where the article will be published;If the oral activity is the modality chosen by the teacher, the student should present his point of view on the topics to the whole class and a debate could start at the end of his presentation.
22 Strategies After 12 Summary Under specific conditions, a stationary object can have energy.General forms of energy, stored in an object, are called potential energies, and according to the force to which they are linked, we have gravitational potential energy, which is the work done by gravity on an object, and elastic potential energy, which is the work done by elastic force on a stretched or compressed spring to return it to its initial position.The forces that do work, are divided into conservative and non conservative forces.A conservative force does work which is independent of the route taken and only depends on the initial position and final position.Gravity and elastic force are conservative forces.So, the work done by a conservative force through a closed route is always zero.A force is called non conservative if its work depends on the chosen route, between the initial position and the final position.
23 Strategies AfterFriction is a non conservative force: it always opposes motion and does negative work that is not stored as potential energy but is transformed into sound or thermal energy.In physics mechanical energy of an object is the sum of its potential and kinetic energies.It is conserved only in the systems where conservative forces are involved:in fact, kinetic energy is transformed into potential energy, just as potential energy is transformed into kinetic energy.In a system with no conservative forces, the mechanical energy can change, as in the case of friction where mechanical work is transformed into sound or thermal energy.In this cases the Law of energy conservation is no longer valid.Answer to the following questions. The questions could be answered in a written or oral form, depending on the teacher’s objectives.
24 Strategies AfterIn addition to kinetic energy, which other forms of energy do you know?How do you define gravitational potential energy and elastic potential energy?When is a force called conservative?Is the work done by a force always equal to zero?Which are the features of a non conservative force?What kind of force is friction?When is mechanical energy conserved?Is a roller coaster an example of energy conservation?What is the work done by non conservative force equal to?2. Write a short abstract of the summary (max 150 words) highlighting the main points of the video.
25 Web References http://www.physics.org/aboutus.asp physics.org is brought to you by the physics in society team at the Institute of Physics. Our aim is to inspire people of all ages about physics. Let us be your guide and show you the best physics places on the web.NASPE's mission is to enhance knowledge, improve professional practice, and increase support for high quality physical education, sport, and physical activity programs.This site was honored because of its comprehensive coverage of most of physics, the creative use of multimedia and linking, and the impact it has had on students worldwide. Online tutorials cover a wide range of physics topics, including modern physics and astronomy. Material is organized through extensive concept maps.”
26 Activities Based on Problem Solving 13Activities Based on Problem SolvingSolve the following problems :A pendulum of mass m=80 gr and length l=120 cm swings at an angle of 25° to the position of equilibrium.What is the potential energy of the pendulum in this position?1)2)At the circus, during a show, a trapeze artist of mass m=50 Kg, falls down to the safety net from a height of 4.5 m with initial velocity equals to 4.0 m/s.Ignoring air resistance, what is her velocity when she lands on the net?3)An apple falls down vertically and lands on the ground with velocityv=40.0 Km/h. Ignoring air resistance, what is the height h from which it falls?
27 Activities based on Problem Solving Solve the following problems :4)A child is on a swing; when the swing is at its lowest point, its velocity is equal to 2.02 m/s.Ignoring air resistance, what is the maximum height that the child will reach?An object of mass m = 1.80 Kg moves on a rough surface with velocityv=2.00 m/s and, before stopping it compresses a spring of 11.0 cm.If the coefficient of friction is equal to 0.560, what is the spring constant?5)
28 Answer Sheets Keywords Breadth, electric potential energy. Conceptual MapPag 29Multiple Choice:22 m/s; 0.41 m; J; 2 v.Matching:1 K v; 2 U x; 3 U h. A (-104 J); B (-47 J); C (-66 J).True / false:T; F; F; T; T; T.Completion exercise:Work done by gravity on a object and depends only on the height h; stretched or compressed spring and is the work done by elastic force to return the spring to its initial position;it does work which is independent of the route taken and it depends on the initial and final positions;conservative force – motion – negative – into sound or thermal energy;conservative forces;The change of mechanical energy.Problem solving:1) J; 2) 10 m / s; 3) 6.3 m; 4) m; 5) 415 N/m.6-2
29 work done by conservative Answer SheetsConceptual Mapmechanical energypotential energykinetic energygravitationalpotentialenergyelasticpotentialenergywork done by conservativeforces and nonconservative forceswork done byconservative forcesvariation ofmechanical energyenergy conservation
30 Answer Sheets Flow Chart Solution startComplete the flow chart in order to determine the final velocity of a wagon of the Roller Coaster that goes down, without friction, from an initial position A, having height h to the ground, to a final position B, having height h to the ground.determine the initial kinetic energythen the initial potential energyand also the final mechanical energyAso apply the Energy ConservationBend