physics dotpoint hscphysics q&a

Brian Shadwick

HSC PHYSICS

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of Science Press. ABN 98 000 073 861

Science Press 2007First published 2007Reprinted 2007, 2008, 2009, 2010

Science PressPrivate Bag 7023 Marrickville NSW 1475 AustraliaTel: (02) 9516 1122 Fax: (02) 9550 [email protected] www.sciencepress.com.au

Contents

Introduction vVerbs to Watch vi

Dot Points

Space viiMotors and Generators ixFrom Ideas to Implementation xiFrom Quanta to Quarks xiii

Questions

Space 1Motors and Generators 39From Ideas to Implementation 81From Quanta to Quarks 121

Summaries


Answers


Appendix

Data Sheet 282Formula Sheet 283Periodic Table 284

Dot Point HSC Physics iii ContentsScience Press

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Contents iv Dot Point HSC PhysicsScience Press

Introduction

What the book includes

,QWKLVERRN\RXZLOOQGW\SLFDOH[DPLQDWLRQTXHVWLRQVDQGDQVZHUVDVZHOODVVXPPDULHVIRUHDFKGRWSRLQWLQthe Board of Studies syllabus for the following topics in the Year 12 Physics course:

6SDFH 0RWRUVDQG*HQHUDWRUV )URP,GHDVWR,PSOHPHQWDWLRQ )URP4XDQWDWR4XDUNV

Also included are typical experimental results for students to analyse if the third column of the syllabus indicates WKDWVWXGHQWVVKRXOGFDUU\RXWUVWKDQGLQYHVWLJDWLRQV

Format of the book

The book has been formatted in the following way:

1. Main topic statement (column 1 of syllabus)

1.1etc Syllabus requirement from columns 2 and 3.

1RWHWKDWWKHQXPEHULQJRIWKHVHUHTXLUHPHQWVLVWKHDXWKRUVFKRLFHDQGKDVEHHQXVHGWRPDNHUHIHUHQFLQJTXHVWLRQVDQGDQVZHUVFOHDUHU7KHLQGLYLGXDOUHTXLUHPHQWVDUHQRWQXPEHUHGLQWKHV\OODEXVWKH\DUHVLPSO\EXOOHWHGKHQFHRXUXVHRIGRWSRLQWVZKHQZHUHIHUWRWKHP

1.1.1 )LUVWW\SLFDOTXHVWLRQZKLFKFRXOGEHDVNHGLQDQH[DPLQDWLRQIRUWKLVV\OODEXV UHTXLUHPHQW1.1.2 6HFRQGW\SLFDOTXHVWLRQZKLFKFRXOGEHDVNHGLQDQH[DPLQDWLRQIRUWKLVV\OODEXV UHTXLUHPHQWHWF

7KHQXPEHURIOLQHVSURYLGHGIRUHDFKDQVZHUJLYHVDQLQGLFDWLRQRIKRZPDQ\PDUNVWKHTXHVWLRQPLJKWEHworth in an examination. As a rough rule, every two lines of answer might be worth one mark. Note that in many DQVZHUVWKUHHOLQHVKDYHEHHQSURYLGHGDVWKHDPRXQWRIZULWLQJUHTXLUHGH[FHHGVWZROLQHVEXWWKHSK\VLFVinvolved is worth only one mark.

How to use the book

&RPSOHWLQJDOOTXHVWLRQVZLOOSURYLGH\RXZLWKDVXPPDU\RIDOOWKHZRUN\RXQHHGWRNQRZIURPWKHV\OODEXVYou may have done work in addition to this with your teacher as extension work. Obviously this is not covered, but you may need to know this additional work for your school exams.

:KHQZRUNLQJWKURXJKWKHTXHVWLRQVZULWHWKHDQVZHUV\RXKDYHWRORRNXSLQDGLIIHUHQWFRORXUWRWKRVH\RXNQRZZLWKRXWKDYLQJWRUHVHDUFKWKHZRUN7KLVZLOOSURYLGH\RXZLWKDTXLFNUHIHUHQFHWRZRUN\RXVKRXOGspend more time revising later, and allow you to spend your study time more productively.

Dot Point HSC Physics v IntroductionScience Press

account/account for State reasons for, report on, give an account of, narrate a series of events or transactions.

analyse Identify components and the relationships among them, draw out and relate implications.

apply Use, utilise, employ in a particular situation.

appreciate Make a judgement about the value of something.

assess 0DNHDMXGJHPHQWRIYDOXHTXDOLW\RXWFRPHVresults or size.

calculate 'HWHUPLQHIURPJLYHQIDFWVJXUHVRULQIRUPDWLRQclarify Make clear or plain.

classify Arrange into classes, groups or categories.

compare Show how things are similar and different.

construct Make, build, put together items or arguments.

contrast Show how things are different or opposite.

critically (analyse/evaluate) Add a degree or level of accuracy, depth, knowledge DQGXQGHUVWDQGLQJORJLFTXHVWLRQLQJUHHFWLRQDQGTXDOLW\WRDQDQDO\VLVRUHYDOXDWLRQdeduce Draw conclusions.

GHQH 6WDWHWKHPHDQLQJRIDQGLGHQWLI\HVVHQWLDOTXDOLWLHVdemonstrate Show by example.

describe Provide characteristics and features.

discuss Identify issues and provide points for and against.

distinguish Recognise or note/indicate as being distinct or different from, note difference between things.

evaluate Make a judgement based on criteria.

examine ,QTXLUHLQWRexplain Relate cause and effect, make the relationship between things evident, provide why and/or how.

extract Choose relevant and/or appropriate details.

extrapolate Infer from what is known.

identify Recognise and name.

interpret Draw meaning from.

investigate 3ODQLQTXLUHLQWRDQGGUDZFRQFOXVLRQVDERXWjustify Support an argument or conclusion.

outline Sketch in general terms; indicate the main features.

predict Suggest what may happen based on available data.

propose Put forward (a point of view, idea, argument, suggestion etc) for consideration or action.

recall Present remembered ideas, facts or experiences.

recommend Provide reasons in favour.

recount Retell a series of events.

summarise Express concisely the relevant details.

synthesise Put together various elements to make a whole.

Verbs to Watch

Verbs to Watch vi Dot Point HSC PhysicsScience Press

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1. *UDYLWDWLRQDOHOG 2 'HQHZHLJKWDVWKHIRUFHDFWLQJRQ DQREMHFWGXHWRDJUDYLWDWLRQDOHOG 1.2 Use F = mg to determine the weight force of bodies on Earth and other planets. 21.3. Predict the acceleration due to gravity on other planets. 31.4 Perform an experiment to determine the acceleration due to gravity and identify reasons for possible variations from 9.8 m s2. 41.5 Explain that a change in gravitational potential energy is related to work done. 6 'HQHGPE as the work done to move DQREMHFWIURPLQQLW\WRDSRLQWLQD JUDYLWDWLRQDOHOG 2. Rocket launches and gravity 92.1 Describe the trajectory of a projectile ZLWKLQWKH(DUWKVJUDYLWDWLRQDOHOG 'HVFULEH*DOLOHRVDQDO\VLVRISURMHFWLOH motion. 92.3 Solve projectile motion problems using horizontal and vertical components DQG1HZWRQVHTXDWLRQVRIPRWLRQ 2.4 Explain escape velocity in terms of the gravitational constant, and the mass and radius of the planet. 11 2XWOLQH1HZWRQVFRQFHSWRIHVFDSH velocity. 12 ,GHQWLI\ZK\WKHWHUPJIRUFHVLV used to explain the forces on an astronaut. 122.7 Perform an experiment to calculate WKHLQLWLDODQGQDOYHORFLWLHVUDQJH DQGWLPHRILJKWRIDSURMHFWLOH 2.8 Analyse the changing acceleration of a rocket during launch in terms of the Law of Conservation of Momentum and the forces experienced by astronauts. 14 'LVFXVVWKHHIIHFWRIWKH(DUWKVRUELWDO and rotational motion on rocket launches. 16

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2.10 Analyse forces involved in uniform circular motion for a range of objects, including satellites orbiting Earth. 172.11 Solve problems about the centripetal force on a satellite in Earth orbit using: 17 &RPSDUHTXDOLWDWLYHO\ORZ(DUWKDQG geostationary orbits. 182.13 Outline the contribution to space of one of: Tsiolkovsky, Oberth, Goddard, (VQDXOW3HOWHULH21HLOORUYRQ%UDXQ 'HQHRUELWDOYHORFLW\DQGLWV relationship with G, the mass of the planet and satellite, and the radius RIWKHRUELWTXDOLWDWLYHO\DQG TXDQWLWDWLYHO\ 6ROYHSUREOHPVXVLQJ.HSOHUV/DZ of Periods. 212.16 Account for the orbital decay of satellites in LEO. 232.17 Discuss issues associated with safe UHHQWU\LQWRWKH(DUWKVDWPRVSKHUH and landing on the surface. 232.18 Identify that there is an optimum angle IRUUHHQWU\LQWRWKH(DUWKVDWPRVSKHUH DQGWKHFRQVHTXHQFHVRIIDLOLQJWR achieve this. 243. The Solar System and gravity 25 'HVFULEHDJUDYLWDWLRQDOHOGQHDUD massive object in terms of its effects on other masses. 25 'HQH1HZWRQV/DZRI8QLYHUVDO Gravitation. 253.3 Solve problems and analyse information using: 25

3.4 Discuss factors affecting the strength of the gravitational force. 27 'LVFXVVWKHLPSRUWDQFHRI1HZWRQV Law of Universal Gravitation in understanding and calculating the motion of satellites. 28

Space

Dot Point HSC Physics vii SpaceScience Press

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3.6 Identify that a slingshot effect can be provided by planets for space probes. 284. Understanding time and space 294.1 Outline the features of the aether model for the transmission of light. 294.2 Describe and evaluate the 0LFKHOVRQ0RUOH\H[SHULPHQW 4.3 Interpret the results of the 0LFKHOVRQ0RUOH\H[SHULPHQW 4.4 Discuss the role of the 0LFKHOVRQ0RUOH\H[SHULPHQWLQ making determinations about competing theories. 304.5 Outline the nature of inertial frames of reference. 304.6 Perform an investigation to distinguish EHWZHHQQRQLQHUWLDODQGLQHUWLDO frames of reference. 314.7 Discuss the principle of relativity. 32 'HVFULEHWKHVLJQLFDQFHRIWKH DVVXPSWLRQRI(LQVWHLQVDVVXPSWLRQ of the constancy of the speed of light. 32 $QDO\VHDQGLQWHUSUHWVRPHRI(LQVWHLQV thought experiments about mirrors and trains and discuss the relationship between thought and reality. 324.10 Identify that if c is constant, then space and time become relative. 334.11 Discuss the concept that length standards DUHGHQHGLQWHUPVRIWLPHLQFRQWUDVW to the original metre standard. 33

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4.12 Discuss the relationship between theory and the evidence supporting LWXVLQJ(LQVWHLQVSUHGLFWLRQVEDVHG on relativity that were made many years before evidence was available to support it. 33 ([SODLQTXDOLWDWLYHO\WKHFRQVHTXHQFH of special relativity in relation to the relativity of simultaneity. 34 ([SODLQTXDOLWDWLYHO\WKHFRQVHTXHQFH RIVSHFLDOUHODWLYLW\WRWKHHTXLYDOHQFH of mass and energy. 344.15 Solve problems using: 34 ([SODLQTXDOLWDWLYHO\WKHFRQVHTXHQFH of special relativity in relation to mass. 354.17 Solve problems using the relativistic PDVVHTXDWLRQ ([SODLQTXDOLWDWLYHO\WKHFRQVHTXHQFH of special relativity in relation to length contraction. 364.19 Solve problems using the relativistic OHQJWKHTXDWLRQ ([SODLQTXDOLWDWLYHO\WKHFRQVHTXHQFH of special relativity in relation to time dilation. 374.21 Solve problems using the time GLODWLRQHTXDWLRQ 4.22 Discuss implications of mass increase, time dilation, length contraction for space travel. 38Answers to Space 237

Space viii Dot Point HSC PhysicsScience Press

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1. Current-carrying conductors 401.1 Discuss the effect, on the force on a FXUUHQWFDUU\LQJFRQGXFWRURI variations in: WKHPDJQHWLFHOGLQZKLFKLWLVORFDWHG WKHFXUUHQWLQWKHFRQGXFWRU WKHOHQJWKRIWKHFRQGXFWRULQWKHHOG WKHDQJOHEHWZHHQWKHPDJQHWLFHOG

and conductor. 401.2 Solve problems and analyse information about the force on FXUUHQWFDUU\LQJFRQGXFWRUVLQ PDJQHWLFHOGVXVLQJ 40 'HVFULEHTXDOLWDWLYHO\DQGTXDQWLWDWLYHO\ the force between long, parallel currentcarrying conductors using:

411.4 Solve problems using:

421.5 Describe the forces experienced by a FXUUHQWFDUU\LQJORRSLQDPDJQHWLF HOGDQGGHVFULEHWKHQHWUHVXOWRI the forces. 431.6 Perform an experiment to demonstrate the motor effect. 44 'HQHWRUTXHDVWKHWXUQLQJPRPHQW of a force using: T 451.8 Solve problems and analyse information about simple motors using: T 461.9 Identify the motor effect is due to the IRUFHDFWLQJRQDFXUUHQWFDUU\LQJ FRQGXFWRULQDPDJQHWLFHOG 1.10 Describe the application of the motor effect in a galvanometer. 471.11 Describe the application of the motor effect in a loudspeaker. 481.12 Describe the main features of a DC electric motor and the role of each feature. 49

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,GHQWLI\WKDWWKHPDJQHWLFHOGLQ '&PRWRUVFDQEHSURGXFHGE\FXUUHQW carrying coils or permanent magnets. 502. Generating electricity 51 2XWOLQH)DUDGD\VGLVFRYHU\RIWKH generation of electricity by a moving magnet. 512.2 Perform an investigation to model the generation of an electric current by moving a magnet in a coil or a coil near a magnet. 522.3 Plan and perform an experiment to predict and verify the effect on a generated current of the distance between the coil and the magnet, the strength of the magnet, and the relative motion between the coil and the magnet. 52 'HQHPDJQHWLFHOGVWUHQJWKB as PDJQHWLFX[GHQVLW\ 'HVFULEHPDJQHWLFX[LQWHUPVRI PDJQHWLFX[GHQVLW\DQGVXUIDFHDUHD 2.6 Describe generated potential difference DVWKHUDWHRIFKDQJHRIPDJQHWLFX[ $FFRXQWIRU/HQ]V/DZLQWHUPVRI conservation of energy. 54 5HODWH/HQ]V/DZWRWKHSURGXFWLRQ of back emf in motors and that this opposes the supply emf. 552.9 Explain production of eddy currents LQWHUPVRI/HQ]V/DZ 2.10 Explain how induction is used in cooktops. 622.11 Explain how eddy currents are used in electromagnetic braking. 623. Generators 633.1 Describe the main components of a generator. 633.2 Describe the differences between DC and AC generators. 63

Motors and Generators

Dot Point HSC Physics ix Motors and GeneratorsScience Press

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3.3 Compare the structure and function of a motor and a generator. 653.4 Discuss advantages and disadvantages of AC and DC generators and relate these to their use. 663.5 Perform an experiment to demonstrate the production of an alternating current. 663.6 Discuss energy losses that occur in transmission lines. 663.7 Assess the effects of the development of AC generators on society. 673.8 Assess the effects of the development of AC generators on the environment. 673.9 Analyse the competition between Edison and Westinghouse to supply electricity to cities. 673.10 Identify how transmission lines are insulated from supporting structures and protected from lightning. 694. Transformers 714.1 Describe the purpose of transformers in electrical circuits. 71 &RPSDUHVWHSXSDQGVWHSGRZQ transformers. 714.3 Identify the relationship between the ratio of the number of turns in the primary and secondary coils and the ratio of the primary to secondary voltage. 72

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4.4 Solve problems using:

724.5 Discuss how the heating effects of eddy currents are minimised in transformers. 744.6 Perform an experiment to model the structure and working of a transformer. 744.7 Discuss the need for transformers in electricity transmission from source to point of use. 754.8 Explain why voltage transformations are related to conservation of energy. 754.9 Discuss why some electrical appliances in the home use transformers. 764.10 Discuss the impact of the development of transformers on society. 765. Motors and energy changes 775.1 Describe the main features of an AC electric motor. 775.2 Perform an investigation to demonstrate the principle of an AC induction motor. 785.3 Identify some of the energy transformations involving the conversion of electrical energy that occur in homes and industry. 79Answers to Motors and Generators 247

Motors and Generators x Dot Point HSC PhysicsScience Press

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1. Cathode rays 821.1 Explain that cathode ray tubes allowed the manipulation of charged particles. 821.2 Explain why the apparent behaviour of cathode rays caused debate as to whether they were charged particles or electromagnetic waves. 821.3 Perform an investigation to identify properties of cathode rays using discharge tubes containing: D0DOWHVHFURVV HOHFWULFSODWHV DXRUHVFHQWVFUHHQ DJODVVZKHHO and analyse the information to determine the sign of the charge on cathode rays. 831.4 Perform an investigation to observe the different patterns of striations in cathode ray tubes at different pressures. 841.5 Identify that moving charged particles LQDPDJQHWLFHOGH[SHULHQFHDIRUFH 'LVFXVVTXDOLWDWLYHO\WKHHOHFWULFHOG strength due to point, positive and negative charges. 851.7 Identify that charged plates produce DQHOHFWULFHOG 'LVFXVVTXDOLWDWLYHO\WKHHOHFWULFHOG strength due to oppositely charged parallel plates. 87 'HVFULEHTXDQWLWDWLYHO\WKHIRUFHRQ a moving charged particle in a PDJQHWLFHOGDQGVROYHSUREOHPV using: F = qE

F = qvBsin 871.10 Outline the experiment by Thomson to measure the charge/mass ratio of an electron. 90

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1.11 For cathode ray tubes, outline the role of: WKHHOHFWURGHVLQWKHHOHFWURQJXQ WKHGHHFWLRQSODWHVRUFRLOV WKHXRUHVFHQWVFUHHQ 2. The photoelectric effect and black body radiation 93 2XWOLQH+HUW]VH[SHULPHQWLQ measuring the speed of radio waves and how they relate to light waves. 93 'HVFULEH+HUW]VREVHUYDWLRQRIWKH effect of a radio wave on a receiver and the photoelectric effect he produced but failed to investigate. 942.3 Perform an experiment to show the production and reception of radio waves. 94 ,GHQWLI\3ODQFNVK\SRWKHVLVWKDW radiation emitted and absorbed by the ZDOOVRIDEODFNERG\LVTXDQWLVHG ,GHQWLI\(LQVWHLQVFRQWULEXWLRQWR TXDQWXPWKHRU\DQGLWVUHODWLRQWR black body radiation. 96 $VVHVV(LQVWHLQVFRQWULEXWLRQWR TXDQWXPWKHRU\DQGLWVUHODWLRQWR black body radiation. 982.7 Explain the particle model of light in terms of photons with particular energy DQGIUHTXHQF\ 2.8 Identify the relationships between SKRWRQHQHUJ\IUHTXHQF\VSHHGRI light and wavelength using: and 992.9 Solve problems using: and 992.10 Summarise the use of the photoelectric effect in solar cells and photocells. 101 'LVFXVV(LQVWHLQDQG3ODQFNV GLIIHULQJYLHZVDERXWZKHWKHUVFLHQWLF research is removed from social and political forces. 102

From Ideas to Implementation

Dot Point HSC Physics xi From Ideas to ImplementationScience Press

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3. Transistors 103

3.1 Identify that some electrons in solids are shared between atoms and move freely. 103

3.2 Describe, in terms of band structures and relative electrical resistance, the differences in conductors, insulators, semiconductors. 103

3.3 Identify absences of electrons in nearly full bands as positive holes, and recognise that electrons and holes help to carry current. 105 &RPSDUHTXDOLWDWLYHO\WKHUHODWLYH number of free electrons in conductors, semiconductors and insulators. 1073.5 Perform an experiment to model the behaviour of semiconductors. 1073.6 Identify that the use of germanium in early transistors was related to the inability to produce other materials of suitable purity. 1083.7 Describe how doping a semiconductor can change its electrical properties. 108 ,GHQWLI\GLIIHUHQFHVLQSDQGQW\SH semiconductors in terms of their relative numbers of negative charge carriers and positive holes. 1093.9 Describe differences between solid state and thermionic devices and why solid state replaced thermionic devices. 1093.10 Discuss how shortcomings in communications technology led to an increased knowledge of the properties of materials with reference to the invention of transistors. 1103.11 Assess the impact of transistors on society with particular reference to their use in microchips and microprocessors. 1103.12 Identify data sources, gather, process and present information to summarise the effect of light on semiconductors in solar cells. 110

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4. Superconductors 115

4.1 Outline the methods used by the Braggs to determine crystal structure. 115

4.2 Identify that metals possess a crystal lattice structure. 1154.3 Describe conduction in metals as a movement of free electrons unimpeded by the lattice. 1154.4 Identify that resistance in metals is increased by the presence of impurities and scattering of electrons by lattice vibrations. 1154.5 Describe the occurrence in superconductors below their critical temperature of a population of electron pairs unaffected by electrical resistance. 1164.6 Identify some of the metals, alloys DQGFRPSRXQGVLGHQWLHGDVH[KLELWLQJ superconductivity and their critical temperatures. 1164.7 Discuss the BCS theory. 1164.8 Discuss the advantages of using superconductors and identify limitations to their use. 1174.9 Explain why a magnet is able to hover above a superconducting material below its critical temperature. 1184.10 Perform an investigation to demonstrate magnetic levitation. 1194.11 Describe how superconductors and WKHHIIHFWVRIPDJQHWLFHOGVKDYH been applied to develop a maglev train. 1194.12 Discuss possible applications of superconductivity and the effects of those applications on computers, generators, motors and the transmission of electricity through transmission grids. 120Answers to From Ideas to Implementation 259

From Ideas to Implementation xii Dot Point HSC PhysicsScience Press

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1. Models of the atom 1221.1 Discuss the Rutherford model of the atom. 122 $QDO\VHWKHVLJQLFDQFHRIWKH hydrogen spectrum in the development of the Bohr model. 1221.3 Perform an experiment to observe the visible components of the hydrogen spectrum. 123 'LVFXVV3ODQFNVFRQWULEXWLRQWRWKH FRQFHSWRITXDQWLVHGHQHUJ\ 'HQH%RKUVSRVWXODWHV 'HVFULEHKRZ%RKUVSRVWXODWHVOHG to a mathematical model to account for the hydrogen spectrum. 1251.7 Solve problems and analyse information using:

1251.8 Process and present diagrams to show %RKUVH[SODQDWLRQRIWKH%DOPHUVHULHV 1.9 Discuss the limitations of the Bohr model of the hydrogen atom. 130 ,GHQWLI\GLIFXOWLHVZLWKWKH%RKU model, including its inability to explain spectra of larger atoms, LQWHQVLW\RIDQGK\SHUQHVSHFWUDO lines and the Zeeman effect. 1302. Development of quantum physics 131 'HVFULEHWKHLPSDFWRIGH%URJOLHV proposal that any kind of particle has both wave and particle properties. 1312.2 Solve problems and analyse information using:

131

'HQHGLIIUDFWLRQDQGLGHQWLI\WKDW interference occurs between waves that have been diffracted. 132 'HVFULEHWKHFRQUPDWLRQRIGH%URJOLHV proposal by Davisson and Germer. 133

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2.5 Explain the stability of the electron orbits in the Bohr atom using GH%URJOLHVK\SRWKHVLV 2.6 Assess the contribution made by Heisenberg and Pauli to atomic theory. 1343. Development of nuclear physics 135 'HQHWKHFRPSRQHQWVRIWKHQXFOHXV and contrast their properties. 1353.2 Discuss the importance of the FRQVHUYDWLRQODZVWR&KDGZLFNV discovery of the neutron. 135 'HQHWKHWHUPQXFOHDUWUDQVPXWDWLRQ 3.4 Describe nuclear transmutations due to natural radioactivity. 137 'HVFULEH)HUPLVLQLWLDOH[SHULPHQWDO REVHUYDWLRQRIQXFOHDUVVLRQ 3.6 Perform an experiment to observe radiation emitted from a nucleus using a Wilson cloud chamber or similar device. 139 'LVFXVV3DXOLVLGHDRIWKHWKH neutrino and the need to account for WKHHQHUJ\HOHFWURQVHPLWWHGLQGHFD\ 3.8 Evaluate the relative contribution of electrostatic and gravitational forces between nucleons. 1413.9 Account for the need for the strong nuclear force and describe its properties. 1413.10 Explain the concept of mass defect XVLQJ(LQVWHLQVHTXLYDOHQFHEHWZHHQ mass and energy. 1423.11 Solve problems to calculate the mass defect and energy released in natural WUDQVPXWDWLRQDQGVVLRQUHDFWLRQV 'HVFULEH)HUPLVGHPRQVWUDWLRQVRI a nuclear chain reaction in 1942. 146 &RPSDUHUHTXLUHPHQWVIRUFRQWUROOHG and uncontrolled chain reactions. 147

From Quanta to Quarks

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4. Applications of nuclear physics 1514.1 Explain the basic principles of a VVLRQUHDFWRU $VVHVVWKHVLJQLFDQFHRIWKH Manhattan Project to society. 1534.3 Describe some medical and industrial applications of radioisotopes. 1534.4 Describe the use of a named isotope in medicine, agriculture, and engineering. 1544.5 Describe how neutron scattering is used as a probe by referring to the properties of neutrons. 155

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4.6 Identify ways by which physicists continue to develop their understanding of matter using accelerators as a probe to investigate the structure of matter. 1554.7 Discuss the key features and components of the standard model RIPDWWHULQFOXGLQJTXDUNVDQGOHSWRQV Answers to From Quanta to Quarks 271

From Quanta to Quarks xiv Dot Point HSC PhysicsScience Press

Dot Point HSC Physics 1 SpaceScience Press

DOT POINTSpace

Space 2 Dot Point HSC PhysicsScience Press

1. The Earth has a gravitational eld that exerts a force on objects both on it and around it.

'HQHZHLJKWDVWKHIRUFHDFWLQJRQDQREMHFWGXHWRDJUDYLWDWLRQDOHOG1.1.1 Predict the weight of a 5 kg object on Earth compared to its weight on Jupiter, and explain the

reasoning behind your prediction. The gravitational acceleration on Jupiter is about 24.8 m s2.

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1.1.2 Complete the table to compare mass and weight.

Mass Weight

1.2 Use F = mg to determine the weight force of bodies on Earth and other planets.

1.2.1 Determine the weight of an object of mass 3.0 kg on Earth and on Mars which has a JUDYLWDWLRQDODFFHOHUDWLRQHTXDOWRWKDWRI(DUWK

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1.2.2 An object has a mass of 12 kg on Earth and a weight of 135.24 N on Saturn. Calculate the YDOXHRIWKHDFFHOHUDWLRQGXHWRJUDYLW\RQ6DWXUQDQGWKHREMHFWVZHLJKWRQ(DUWK

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1.2.3 A mass is placed on a set of bathroom scales on Earth and the scales read 10 kg. The same scales and the mass are taken to the Moon to show that the mass of an object is constant regardless of where it is in the Universe. When placed on the scales on the Moon however, the scales read 1.67 kg. Account for this reading.

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1.3 Predict the acceleration due to gravity on other planets.

1.3.1 The table shows masses and diameters of the Sun, our Moon and the planets in the Solar System.

(a) Complete the fourth column of the table by ranking the gravitational force on each object from smallest (1) to largest (11) given the values for the Sun, the Earth and Pluto.

E &RPSOHWHWKHIWKFROXPQRIWKHWDEOHE\SUHGLFWLQJWKHUHODWLYHVL]HRIWKHJUDYLWDWLRQDOIRUFHon each object given the three values for the Moon, Earth and the Sun.

Object Mass of object (kg)Diameter of object

(km)

Gravitational force (smallest (1) to

largest (12))

Gravitational acceleration

(m s2 )

The Sun 1.99 1030 1 392 530 11 275.4

Mercury 3.58 1023 4878

Venus 4.90 1024 12 104

Earth 5.974 1024 12 756 7 9.8

The Moon 7.35 1022 3467 1.6

Mars 6.43 1023 6794

Jupiter 1.90 1027 142 984

Saturn 5.69 1026 120 000

Uranus 8.68 1025 51 800

Neptune 1.03 1026 49 250

Pluto 1.27 1022 2320 1

1.3.2 An object has a mass of 60 kg on Mars where the gravitational acceleration is 0.38 that of Earth.

(a) What will be the mass of the object on Mars?

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(b) What will be the weight of the object on Earth?

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(c) What will be the weight of the object on Mars?

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(d) What will be the mass of the object on a planet where the acceleration due to gravity is 2.5 times larger than that on Earth?

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(e) What will be the weight of the object on this planet?

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1.4 Perform an experiment to determine the value of the acceleration due to gravity and identify reasons for possible variations from 9.8 m s2.

1.4.1 Outline an experiment you have done to determine the acceleration due to gravity.

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1.4.2 A group of students set up a pendulum and recorded the measurements shown in the table.

Length of pendulum string (m)

Time for 20 swings (s) Period of swing (s) (Period of swing)2 (s2)

0.25 0.50 0.75 1.00 1.25 1.50 2.00

20.0 28.2 38.6 40.0 44.9 49.9 56.5

(a) Identify two factors which would have been kept constant if this experiment had been done correctly.

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(b) Complete the results table.


(c) What are these results telling us?

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(d) Draw a graph of the period of swing (T) against the length of the pendulum (l).

(e) What conclusion can we draw from this graph? Explain your answer.

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I ,QGUDZLQJ\RXUOLQHRIEHVWW\RXVKRXOGKDYHLJQRUHGRQHSORWSRLQW,GHQWLI\ZKLFKSORWpoint and explain why it should be ignored.

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J 7KHHTXDWLRQFRQQHFWLQJWKHYDULDEOHVIRUWKHVZLQJRIDSHQGXOXPLV 5HDUUDQJHWKLVHTXDWLRQWRPDNHJWKHVXEMHFW

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K 8VHWKHLQIRUPDWLRQLQ\RXUUHDUUDQJHGHTXDWLRQDQGWKHGDWDLQWKHUHVXOWVWDEOHWRGUDZDgraph which does show the relationship between the period of a pendulum and its length.

(i) Use your graph to determine a value for the acceleration due to gravity as found by this experiment.

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T = 2 lg


1.4.3 Recall three reasons why the acceleration due to gravity at different places on the surface of the Earth varies slightly from the 9.8 m s2 value we usually use.

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1.5 Explain that a change in gravitational potential energy is related to work done.

1.5.1 Explain the relationship between the work done on an object which changes its position in a JUDYLWDWLRQDOHOGDQGLWVJUDYLWDWLRQDOSRWHQWLDOHQHUJ\

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1.5.2 Identify the source of the work done when a satellite moves:

(a) to a higher altitude orbit

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(b) to a lower altitude orbit

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1.5.3 A satellite has 4000 J of work done on it. Does it move to a higher or lower altitude orbit? Explain your answer.

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1.5.4 A comet approaches the Sun and swings around it to travel back into the outer Solar System for years. The graphs show how the gravitational potential and kinetic energies of this comet change as it moves away from the Sun. Explain the shape of the two graphs.

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'HQHJUDYLWDWLRQDOSRWHQWLDOHQHUJ\DVWKHZRUNGRQHWRPRYHDQREMHFWIURPLQQLW\WRDSRLQWLQDJUDYLWDWLRQDOHOG1.6.1 Calculate the gravitational potential energy of a 2000 kg satellite which

orbits the Earth at an altitude of 35 000 km. The radius of Earth is 6378 km.

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1.6.2 A satellite of mass 500 kg is boosted from an orbit of altitude 10 000 km to one of altitude 20 000 km. Given the diameter of Earth as 12 756 km, its mass as 5.97 1024 kg, calculate the change in the gravitational potential energy of the satellite.

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KE

Ep

0

+

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1.6.3 Explain, in terms of the principles of physics involved, why gravitational potential energy is a QHJDWLYHTXDQWLW\

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1.6.4 Satellite X has its orbit around Earth changed from an altitude of 10 000 km to an altitude of 20 000 km. Satellite Y has its orbit around Earth changed from an altitude of 20 000 km to an altitude of 30 000 km. Both satellites have a mass of 500 kg.

(a) Predict the amount of work done on X compared to the amount done on Y and explain your reasoning.

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(b) Calculate the amount of work done on each satellite to see if your prediction was correct.

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1.6.5

(a) Three spacecraft having masses m1 > m2 > m3 are in the same stable orbit around planet X. Compare their gravitational potential energies and justify your answer.

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(b) The three spacecraft are now moved to an orbit with twice the radius relative to the centre of the planet. Compare the work which needs to be done on each. Justify your answer.

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(c) The three spacecraft each undergo orbital decay and fall to identical lower altitude orbits. Compare the changes in their kinetic energies. Justify your answer.

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2. Many factors have to be taken into account to achieve a successful rocket launch, to maintain a stable orbit and to return to Earth.

2.1 Describe the trajectory of an object undergoing projectile motion within the Earths JUDYLWDWLRQDOHOG2.1.1 Outline the characteristics of the motion of a projectile.

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2.1.2 A projectile is launched at 40 m s1 at 75 to the horizontal. Calculate the components of its launch velocity.

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2.2 Describe Galileos analysis of projectile motion.

2.2.1 /LVW*DOLOHRVWKUHHQGLQJVUHJDUGLQJSURMHFWLOHPRWLRQ ...............................................................................................................................................................................................................................

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2.2.2 The table shows the results of an experiment where a ball was rolled along a smooth, horizontal surface at 15 m s1 and then over the edge of a 150 m drop. The ball left the surface and started to fall at time zero.

Time (s) Speed of ball (m s1)

1 17.92

2 24.68

3 33.01

4 41.97


'HPRQVWUDWHWKDWWKHVHUHVXOWVDUHFRQVLVWHQWZLWK*DOLOHRVDQDO\VLVRISURMHFWLOHPRWLRQ ...............................................................................................................................................................................................................................

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2.3 Solve projectile motion problems using horizontal and vertical components and Newtons equations of motion.

2.3.1 $SURMHFWLOHLVUHGKRUL]RQWDOO\DWPV1 from the top of a 196 m high cliff. Calculate:D LWVWLPHRILJKW

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(b) its range

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(c) its velocity on hitting the ground

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2.3.2 $SURMHFWLOHKDVDWLPHRILJKWRIVDQGDUDQJHRIP&DOFXODWH(a) its horizontal velocity

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(b) its maximum height

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(c) the velocity with which it is projected

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2.3.3 $FDQQRQEDOOLVUHGDWPV1 at an angle of 45 to the horizontal. Calculate the height at which the ball hits a vertical cliff 150 m away.

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2.4 Explain the concept of escape velocity in terms of the gravitational constant, and the mass and radius of the planet.

2.4.1 .QRZLQJWKDWWKHZRUNGRQHRQDQREMHFWGLVSODFHGLQDJUDYLWDWLRQDOHOGLVHTXDOWRLWVFKDQJHLQJUDYLWDWLRQDOSRWHQWLDOHQHUJ\DQGWKDWWKLVDOVRHTXDOVLWVFKDQJHLQNLQHWLFHQHUJ\show that escape velocity is independent of the mass of the object being put into orbit.

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2.4.2 The escape velocity of Earth is 11.2 kps. That for Neptune is 23.6 kps. Give possible reasons to account for this difference.

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2.4.3 Mercury has a mass of 3.58 1023 kg and a diameter of 4880 km. Venus has a mass of 4.92 1024 kg and a diameter of 12 104 km. Predict which has the greater escape velocity and explain your reasoning.

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2.5 Outline Newtons concept of escape velocity.

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