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Contents

Amusement park physics . . . . . . . . .1

Car audio . . . . . . . . . . . . . . . . . . . . . .22

Cars—speed and safety . . . . . . . . . .47

Crime scene physics . . . . . . . . . . . . .70

Discovering the Solar System . . . . .93

Electronic devices . . . . . . . . . . . . . .113

Medical physics . . . . . . . . . . . . . . . .135

Movie magic . . . . . . . . . . . . . . . . . . .155

Physics in the home . . . . . . . . . . . .176

Rocket science . . . . . . . . . . . . . . . . .202

Sport . . . . . . . . . . . . . . . . . . . . . . . . .232

The search for understanding . . .251

The sounds of music . . . . . . . . . . .273

Visiting the reef . . . . . . . . . . . . . . . .294

1 Acceleration . . . . . . . . . . . . . . .319

2 Atomic structure . . . . . . . . . . .323

3 Bernoulli’s principle . . . . . . . .330

4 Buoyancy . . . . . . . . . . . . . . . . . .334

5 Capacitors and inductors . . . .338

6 Centre of mass . . . . . . . . . . . . .345

7 Charge and Coulomb’s law . .347

8 Circular motion . . . . . . . . . . . .350

9 Collisions . . . . . . . . . . . . . . . . . .352

10 Critical velocity . . . . . . . . . . . . .358

11 Density . . . . . . . . . . . . . . . . . . . .360

12 Direction . . . . . . . . . . . . . . . . . .363

13 Electric fields and potential . .365

14 Electricity . . . . . . . . . . . . . . . . . .371

15 Electromagnetic spectrum . . .377

16 Energy and work . . . . . . . . . . .379

17 Equations of motion . . . . . . . .384

18 Equilibrium . . . . . . . . . . . . . . . .386

19 Escape velocity . . . . . . . . . . . . .387

20 Fluid flow . . . . . . . . . . . . . . . . . .388

Contexts

Essential Physics

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21 Friction . . . . . . . . . . . . . . . . . . . .392

22 Gravity . . . . . . . . . . . . . . . . . . . .395

23 Heat and its effects . . . . . . . . .399

24 Heat and temperature . . . . . . .403

25 Hooke’s law . . . . . . . . . . . . . . . .407

26 Ideal gas laws . . . . . . . . . . . . . .410

27 Kinetic energy . . . . . . . . . . . . . .419

28 Kinetic theory of a gas . . . . . .421

29 Kirchhoff’s rules . . . . . . . . . . . .426

30 Lasers . . . . . . . . . . . . . . . . . . . . .429

31 Latent heat . . . . . . . . . . . . . . . . .432

32 Lenses . . . . . . . . . . . . . . . . . . . . .434

33 Magnetic fields . . . . . . . . . . . . .445

34 Magnetic forces . . . . . . . . . . . .450

35 Magnetism and electromagnetic induction . .456

36 Mass and weight . . . . . . . . . . . .463

37 Mass–energy equivalence . . .465

38 Mirrors . . . . . . . . . . . . . . . . . . . .468

39 Momentum and impulse . . . .480

40 Newton’s first law of motion .483

41 Newton’s second law of motion . . . . . . . . . . . . . . . . . . . .486

42 Newton’s third law of motion 488

43 Nuclear fission . . . . . . . . . . . . .489

44 Nuclear fusion . . . . . . . . . . . . .492

45 Nuclear radiation . . . . . . . . . . .494

46 Pascal’s principle . . . . . . . . . . .498

47 Pendulum . . . . . . . . . . . . . . . . .501

48 Photoelectric effect . . . . . . . . .504

49 Potential energy . . . . . . . . . . . .509

50 Power—electrical . . . . . . . . . . .513

51 Power—mechanical . . . . . . . . .516

52 Pressure . . . . . . . . . . . . . . . . . . .518

53 Quantum theory . . . . . . . . . . . .523

54 Radioactive decay . . . . . . . . . .525

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Contents

55 Relativity . . . . . . . . . . . . . . . . . .531

56 Rotational motion . . . . . . . . . .536

57 Semiconductors . . . . . . . . . . . .540

58 Simple harmonic motion . . . .545

59 Simple machines . . . . . . . . . . .549

60 States of matter . . . . . . . . . . . . .555

61 Terminal velocity . . . . . . . . . . .557

62 Units . . . . . . . . . . . . . . . . . . . . . .559

63 Vectors . . . . . . . . . . . . . . . . . . . .563

64 Velocity . . . . . . . . . . . . . . . . . . . .570

65 Vertical and projectile motion . . . . . . . . . . . . . . . . . . . .572

66 Waves and refraction . . . . . . . .579

67 Waves and the Doppler effect . . . . . . . . . . . . . . . . . . . . . .586

68 Waves and their speed . . . . . .588

69 Waves in one dimension . . . .594

70 Waves in two dimensions . . . .601

71 Wave–particle duality . . . . . . .608

Appendix A . . . . . . . . . . . . . . . . . . .609

Appendix B . . . . . . . . . . . . . . . . . . .613

Appendix C . . . . . . . . . . . . . . . . . . .614

Answers . . . . . . . . . . . . . . . . . . . . . .615

Index . . . . . . . . . . . . . . . . . . . . . . . . .624

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The following five Essential Physics topics can be found on the

ePhysics CD:

Graphs and tables

Mathematical skills

Measurements and calculations

Problem solving

Writing scientific reports

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The second edition of Heinemann Queensland Science Project—Physics:A Contextual Approach presents physics in a variety of real-world contexts andis designed to support the new Queensland 2007 Physics Syllabus. It is alsosuitable for other physics courses requiring a contextual approach.

The single textbook for both years 11 and 12 provides for flexibility ofplanning, enabling topics to be selected and studied in an order that suits theteachers and students.

The organisation of the new Queensland 2007 Physics Syllabus involvesplanning of a course of study that focuses on general objectives categorised asKnowledge and Conceptual Understanding, Investigative Processes andEvaluating and Concluding. Ten key concepts are the foundation stones of thesyllabus, organised into three themes: Force, Energy and Motion. The keyconcepts are broad statements concerning the fundamental knowledgeunderpinning physics. Any course of study must allow students to develop anunderstanding of each of these key concepts embedded in at least two real-world contexts. Also listed in the syllabus are expansions of the key conceptsidentified as key ideas. These are there to assist teachers understand thebreadth and depth to which the key concepts should be studied.

Heinemann Queensland Science Project—Physics: A Contextual Approach second edition

Physics: A Contextual Approach is structured in two parts:• Contexts—These are the starting point for the development of a course of

study. Physics ideas and concepts are explored in real-life situations.Physics ideas that are specific to a particular situation are developed indetail.

• Essential Physics—Many physics ideas find application in a variety ofcontexts. These are developed separately in a non-context-specific way.

The ContextsContexts are linked to the key ideas within the Essential Physics section viaclear references. Experiments and other activities within a context are aimedat providing practice or actual assessment items according to the assessmentcategories of the syllabus. As students engage with these activities they willdevelop a greater understanding of the key concepts and key ideas from thesyllabus.

Teaching in context means that assessment should also be in context. In the2007 syllabus, three categories of assessment are identified:• Extended Experimental Investigation• Supervised Assessment• Extended Response Task.Activities within the contexts have the potential to be used for assessment andare categorised accordingly.

Introduction......................................................

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Introduction

Essential PhysicsThe Essential Physics topics contain the physical concepts and ideas essential tounderstanding the key concepts and key ideas. They include clearly presentedformulas, definitions and worked examples. Opportunities to use PracticalActivities and Interactive Tutorials are signposted. Each Essential Physics topic hasrelated questions, drawn from a variety of contexts, and answers to these areincluded in the text.

ePhysicsThe ePhysics student CD consists of an electronic version of the textbook, extraEssential Physics topics, Practical Activities for students and fully InteractiveTutorials that model and simulate key physics concepts.

Physics: A Contextual Approach Teacher’sResource and Assessment DiskThe Teacher’s Resource and Assessment Disk includes a copy of the ePhysics studentCD, fully worked solutions to the exercises in the Contexts and to the questions inthe Essential Physics section, experimental notes and safety advice for PracticalActivities, PowerPoint presentations, sample course outlines, sample assessmentitems and criteria sheets. The second edition TRAD also includes a question bankfeaturing hundreds of extra questions all with fully worked solutions and crossreferenced to the Contexts and Essential Physics.

Importantly, sample course outlines demonstrate ways of incorporating therequirements of the syllabus into a course of study presented over years 11 and 12.

Physics: A Contextual Approach can be used as a resource for teachers andstudents as they plan for, and work through, the selected contexts. Sampleassessment tasks are provided for the categories Extended Response Task,Extended Experimental Investigation and Supervised Assessment. Sample criteriasheets for each of these tasks demonstrate how the criteria can be individualisedfor each assessment task but still link closely with the standards associated withthe exit levels of achievement in the syllabus.

About the authorsDavid MaddenDavid has taught senior physics in a variety of school settings in Queensland for over 10 years.He is currently Head of Sciences at St Aidan’s Anglican Girls’ School in Corinda and District PanelChair for the Brisbane–Ipswich District Review Panel for Physics. David has taught physics atschools involved in both the Trial-Pilot and Extended Trial-Pilot of the new physics syllabus.He has presented a number of seminars based on his experience of teaching physics in contextat CONASTA, CONSTAQ and QSA Physics Trial-Pilot conferences. David has a particular interestin the use of valid assessment in context. His other interests include science fiction, cricket andplaying the piano.

Tyson StelzerTyson has 8 years’ experience as an innovative physics teacher at Trinity Lutheran College on theGold Coast and now serves as Head of Senior Science. He has been widely published within theAustralian wine industry, with a particular emphasis on the technicalities of wine science. Tysonhas also written Theme Park Physics, the Teacher Handbook for Dreamworld’s EducationProgramme and is a contributing author to the latest addition to Queensland Science Project,Heinemann Science 10: A Contextual Approach.

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Tracy GazeTracy has 12 years’ experience as an educator in secondary science and mathematics. With acommitment to criteria-based assessment and the development of student skills, she wasinvolved in developing the junior and senior mathematics and science curricula when a newindependent school established itself in Hervey Bay. This involvement included 5 years with soleresponsibility for the physics program at Fraser Coast Anglican College, together withmembership of the QSA Wide Bay District Review Panel for Physics. Tracy has also completed abachelor degree in psychology, and maintains a strong interest in student development.

Ian LindsayIan has over 20 years’ experience as a secondary science and mathematics teacher. He hascontinuously been involved in curriculum design and delivery at a whole-school level as well as atthe subject level in senior physics and junior and senior mathematics. Ian has been Coordinatorof Physics at Runcorn State High School for the last 16 years and in this capacity has been amember of the QSA Physics District Review Panel for 7 years. Ian has always sought to deliverphysics in an engaging and relevant way, and endeavoured to have his students experience the joyof understanding.

Darryl ParsonsDarryl Parsons (MScEd, PostGradDipScEd, GradDipEd(Mgt), GradDipEd, BAppSc, JP(Qual)) hastaught junior science, maths and senior chemistry and physics in Queensland schools for over 20years. He has served on the QSA Physics and Chemistry District Panels for 7 years, has beenScience Master, Assistant Principal and Head of Curriculum, and is currently the Principal of theHills International College in Jimboomba, Queensland.

Acknowledgements

The publisher would like to thank and acknowledge the following people for their contribution tothe first and second editions of this book:Marianne Hammat for her contribution to the structure and organisation of the book, managementof this project, fine editorial work and unwavering commitment to this complex and challengingproject.Brigid Brignell for her professional and committed management of the project.Julia Balcombe for her tireless contribution to the running and management of the project.

David MaddenTo Karen, Jessie and Reuben, thank you for all your support and encouragement. To my Mum andDad, thanks for giving me a love of learning and encouraging me to ask questions.

Ian LindsayThanks to Merv Swords for getting me involved in the co-writing of this book, to MatthewSatterthwaite and Chris Godde for their practical help, and to all those who displayed patiencewhile I progressed through the stages of publishing this book. Specific thanks to my great kids,Jarrah and Nerida, who have been most patient, and also to PK for her encouragement and support.May I dedicate my portion of this book to Col Martin whose infectious enthusiasm for knowledgeand understanding made him such a great teacher.

Darryl ParsonsThanks to my wife Robyn for letting me disappear into my home office for extended periods over thelast two years when I should have been fixing the boat.

Tracy GazeThanks to Mr Greg Lynch, Head of Department (Science) and teacher of Marine Studies at FraserCoast Anglican College, for his support and assistance during the writing process for the context,‘Visiting the Reef ’. Many thanks to my very understanding and very supportive husband Dave,without whose assistance the task of writing while mothering our baby would have been nighimpossible. And finally, a big thank you to Mr Phillip Tann for inspiring my love of physics in thefirst place.

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Practical Activities and Interactive Tutorials

The following Practical Activities and Interactive Tutorials can be found on the ePhysics student CDaccompanying this textbook.

Practical Activities01 Disturbance and propagation of a

disturbance 02 Waves in a Slinky 03 Waves in a rope04 The speed of sound by clap and

echo 05 Waves in a ripple tank 06 Reflection of waves in a ripple

tank 07 Diffraction of continuous water

waves 08 Interference of water waves 09 Reflection in a plane mirror 10 Refraction of continuous water

waves 11 Investigating refraction: Snell’s law 12 Total internal reflection in prisms 13 Colour addition and subtraction 14 Light and a continuous spectrum 15 Polarisation effects with light 16 Concave mirrors 17 Convex lenses 18 Audio transmission with a light

beam 19 Newton’s particle model of light 20 Diffraction of light 21 Interference of light: Young’s

double slits 22 Photoelectric effect 23 Internal resistance of a battery 24 Characteristics of diodes 25 Transistors as amplifiers 26 Solar cell’s response to light 27 Investigating resistors 28 Charge and time constant of

capacitors 29 RC circuits 30 Rectifier circuits 31 Using a zener diode 32 Voltage regulators 33 Specific heat capacity of a metal 34 Power of a tea light 35 Latent heat of fusion of water 36 Specific heat capacity of a brick 37 Solar cooker 38 Solar hot water heater 39 Water purification unit 40 Pitch, loudness and quality 41 Visualising standing waves in air

columns 42 Speed of sound by resonance tube 43 Frequency response of a

loudspeaker 44 Interference of sound 45 Kinematics of a student 46 The ticker timer 47 Analysing motion with a motion

sensor 48 Acceleration down an incline 49 A reaction timer

50 Force and equilibrium 51 Newton’s second law I52 Newton’s second law II 53 Conservation of energy 54 Conservation of momentum in

explosions 55 Locating the centre of mass 56 Graphs of motion57 Action and reaction 58 Motion on an inclined plane 59 Projectile motion 60 Conservation of momentum in

collisions 61 Conservation of energy in springs 62 Hooke’s law: Determining k for a

spring 63 Centripetal force 64 Acceleration due to gravity 65 Frames of reference 66 Relative motion 67 Time dilation 68 The Lorentz factor 69 A non-simultaneity simulation 70 Stress and strain in two rubber

bands 71 Forces in a beam 72 The compressive strengths of

materials 73 An investigation of copper wire 74 Forces in a cantilever 75 Locating the centre of gravity 76 Seesaws 77 Electrostatics with a Van der

Graaff generator 78 Connecting circuits 79 Using electrical meters 80 Resistance and temperature 81 Ohmic and non-ohmic

conductors 82 Electrical power 83 Series circuits 84 Parallel circuits 85 Resistance in a combination

circuit 86 Internal resistance of a dry cell 87 Direction of induced current in a

wire 88 Strength of the magnetic field

inside a coil 89 Investigating electromagnetic

induction 90 Faraday’s law of electromagnetic

induction 91 Current from an electric motor 92 Transformer operation 93 Calculating the charge-to-mass

ratio of an electron 94 A collision in two dimensions 95 Observing the photoelectric effect 96 Wavelength of LEDs 97 Optical fibre bend loss 98 Fibre optic cladding

99 A free space optical transmitter 100 Hydroelectric power 101 Sunlight intensity and reflectivity

of Earth’s surface 102 Solar energy: Generating

electricity I103 Solar energy: Generating

electricity II104 Wind power 105 Solar constant 106 Energy efficiency of a fuel cell107 Detecting radiation with a

Geiger–Müller tube108 The diffusion cloud chamber109 A model of alpha scattering110 An analogue experiment of

radioactive decay111 Ultrasound interactions:

Attenuation of sound112 The Doppler effect I113 Diagnostic X-rays114 Watching the night sky115 Measuring the night sky:

alt-azimuth116 Measuring the night sky:

equatorial coordinates117 The Sun in the day sky118 The phases of the Moon119 Computer simulation of the

night sky120 Night sky exercises in astronomy121 Distances by parallax

measurement122 The inverse square law123 The Doppler effect II124 Spectra of different elements125 LEA and CLEA

Interactive TutorialsBraking (Video analysis of motion)GeneratorsKilowatt-hoursKinetic and gravitational potential

energyMotorsPhotoelectric effect: Frequency versus

kinetic energyPhotoelectric effect: Investigate

forward and reverse voltagePhotoelectric effect: Investigate light

intensityPhotoelectric effect: Which colours will

work?Radioactive decay and half-lifeRefractionRelative velocitiesSpecific heat of a metalThe wave equationsYoung’s modulus

Step 1

.The school selects 6–12 Contexts as U

nits of W

ork or chooses a sam

ple Course Outline

from the TR

AD

Step 2

.The school chooses a variety of learning experiences through w

hich to develop the contexts

Step 3

.The school develops assessm

ent tasks to assess student achievem

ent

Key Concepts

SchoolTextbook

Syllabus

Key IdeasD

efine the depthand scope of theKey Concepts

Criteriaand standards

Assessment

techniquesTeacher’s Resource &

Assessment Disk (TRAD)

Contains sample course

outlines,assessment tasks,

criteria sheets

QuestionsExperim

entsSim

ulationsInvestigations

Essential PhysicsD

evelopment of Key

Concepts and Key Ideas in context is supported using Essential Physicssections

Each key conceptm

ust be covered in at least 2 contexts

Each context coversseveral key concepts

Supervised assessm

entExtendedexperim

entalinvestigation

Extendedresponse task

Force

Energy

Motion

Devising a course of study

Contexts

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:a contextual approachPHYSICS⌧

Key IdeasF1.1, F1.2, F1.3, F1.4F2.3F3.3, F3.4F4.3E1.1, E1.4, E1.5, E1.6E2.5, E2.6E3.1, E3.2, E3.4M2.1, M2.2, M2.3,M2.4M3.1

Essential Physics• Acceleration• Atomic structure

• Collisions • Electromagnetic

spectrum• Energy and work• Friction• Kinetic energy • Lasers• Lenses• Momentum and

impulse• Nuclear fission • Nuclear fusion• Nuclear radiation• Newton’s third law of

motion

• Vertical and projectilemotion

• Velocity• Wave–particle duality

Related EssentialPhysics• Equations of motion• Newton’s first law of

motion• Newton’s second law

of motion

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crime scenephysics

‘Bullets can do incredible things. Things they are not supposed to do.’Sergeant David Taylor of the Texas Police Department was referring to atragic and extraordinary accident at the Dallas Pistol & Revolver Club. Thedate was 29 September 1991. Fourteen-year-old Trey Cooley, a spectatorsitting in the safe area behind the firing line of an air-pistol range, wasstruck in the head and killed by a stray bullet. Investigators were baffled as to where the bullet had come from—so much so that a later televisiondocumentary on the incident was entitled ‘The Magic Bullet’.

Physics experts were called in. Using their knowledge of ballistics, laseranalysis, scale modelling and computer animation they slowly re-created thepath of the errant bullet. The investigators discovered that the bullet hadoriginated at one of the facility’s outdoor ranges, travelled under a woodenvertical baffle, over a four-metre-high impact berm, entered the siding ofthe air-pistol range, passed through a storage room, went through asecond wall inside the building, entered the pistol range, ricocheted off the ceiling and passed through a plaster wall before striking the boy.

figure cp.1 Trey Codeywas shot in the head inthe lobby of his father’sgun club by a misfiredbullet from the outdoorrange. Forensic physicistsreconstructed the bizarrepath of the bullet.

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A–D

Acceleration

When an object speeds up or slows down, it has a change in velocity, which isacceleration. When an object speeds up, it has a positive acceleration. When itslows down, it has a negative acceleration.

Acceleration ......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

11

equation 1.1 a = =

where a is acceleration (m s–2), u is initial velocity and v is final velocity (m s–1),and t1 and t2 are initial and final time (s), respectively.

v − ut2 − t1

∆v∆t

Acceleration is the rate of change of velocity. It iscalculated by subtracting theoriginal velocity from the finalvelocity, and dividing by thetime taken.

¤

See Velocity on page 570.*

See Units on page 559.*

....................................................................................................................................................WWorked example orked example 11..11

A car goes from rest to 80 km h–1 north in 5 s. What is its averageacceleration?

SolutionWe know that u = 0 m s–1, v = 80 km h–1 = 22.2 m s–1, t1 = 0 s andt2 = 5 s. Substituting into equation 1.1:

a = }∆∆vt} = }t

v2

––ut1

} = }22

5.2–

–0

0} = 4.4

Hence, the average acceleration of the car is 4.4 m s–2 north.

Acceleration is a vector with the same direction as the velocity change. If anobject is moving left and changes its velocity so that it is moving right, theacceleration is to the right. If an object is moving left, and continues moving left,but at a slower speed, it has undergone an acceleration to the right, since thevelocity change is to the right.

¤

....................................................................................................................................................WWorked example orked example 11..22

A trolley is rolling at 10 m s–1 to the west. After 3 s, it is rolling west at2 m s–1. What is its acceleration?

SolutionLet west be the positive direction. We have u = 10 m s–1, v = 2 m s–1, t1 = 0 s and t2 = 3 s. Substituting into equation 1.1:

a = }∆∆vt} = }t

v2

––ut1

} = }23

––

100

} = }–38} = –2.7

The negative sign indicates that the acceleration is to the east at2.7 m s–2.

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A–D

Atomic structure

....................

The structure of the atom has been developed step-by-step, beginning with theidentification of the atom itself. The word atom comes from the Greek word for‘indivisible’, and reflects the early theory that all matter was made up of atomswhich were the smallest particles that existed. When J. J. Thomson discoveredthe electron in 1897, this theory had to be adjusted to account for electronsbeing smaller than atoms. Thomson suggested that atoms were a cloud ofpositive charge containing evenly spread negative electrons.

Rutherford’s modelIn 1911, Ernest Rutherford and his team were stunned to find that some of therelatively large positive particles that they fired at gold atoms were scatteredthrough large angles, and were even able to rebound straight back. They hadbeen using a radioactive source to fire alpha particles (which we now know tobe helium nuclei consisting of two protons and two neutrons) at a thin piece ofgold foil, including samples only a few atoms thick (or about 4 × 10–5 cm). Usinga fluorescent screen to detect the alpha particles after scattering, they foundthat most of their results were as expected, but not all.

Atomicstructure

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22

figure 2.1 Alpha particles firedat a thin strip of gold foil can bedetected using a fluorescentscreen.

rotating platform(to rotate screenand microscope)

tube toevacuatechamber

source ofalpha particles(radium)zinc sulfide

screen

microscope gold foil lead box

280CRutherford’s observations:

• Most of the alpha particles passed straight through the foil without beingdeflected.

• Some of the alpha particles were deflected through large angles.

• A few alpha particles rebounded straight back.

Rutherford’s conclusions:

• Most of the atom is empty space, which accounts for the first observation.

• The nucleus is positively charged, which accounts for the secondobservation.

• Almost all of the mass of the atom is concentrated in a nucleus at thecentre, which accounts for the third observation.

Practical activityA model of alpha

scattering 109