2 April 2006 sundayherald 3

EXAM GUIDE

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John O’Brien is currently Principal teacherof Physics in Eastwood High School in EastRenfrewshire. John has worked withGlasgow’s advisory service helping to trainteachers, was a marker and moderator formany years and is currently committed towork as a Verifier with the SQA next year.John is a teacher member of an SQAsubject advisory group consideringalterations to the Scottish Physicscurriculum and is a Secondaryrepresentative on an East RenfrewshireScience Assessment Group.

BY JOHN O’BRIEN ON Wednesday, May 17, thousands ofpeople in Scotland will sit and willpass their Physics Standard Gradeand Higher examination. This guide

is aimed at helping you be part of the groupwhich does well.

Recent changes to the arrangements forpupils sitting examinations in 2006 maymake a difference to how you prepare forthe Physics papers.

For the first time in the Physics exam, allcandidates will have access to a booklet con-taining lists of equations used in the exams.It is essential that you familiarise yourselveswith this booklet and are confident that youcan find all the equations you need quickly.Higher candidates should note that anequation they need might be found in theIntermediate 2 or Standard Grade pages.

You need to be sure that you know what allthe symbols in the equations mean if you aregoing to rely on them. Most teachers wouldadvise you to learn the equations by heartand simply use the list as a safety net. Youwill work more quickly if you know yourequations and don’t have to look them up.

Another change to the exams affects theHigher Radiation and Matter Unit and theIntermediate 2 Radioactivity Unit.

In these units some terms have beenchanged, for example wR (radiationweighting factor) has replaced Q (qualityfactor) in problems, so what was previouslyH = D x Q now becomes H = D x wR.n Intensity (I) has been changed toIrradiance (I).n Quality factor, Q, has been changed toradiation weighting factor, wR.

n Dose equivalent has been changed toequivalent dose.n H = D x Q has been changed to H = D x wRin the marking instructions.

Intermediate 2 students will have a datasheet of physical constants given out at thestart of their examination, rather than databeside the questions. The data booklet willbe similar to that used in Standard Grade,except that it will not have prefixes such asmilli, Mega and so on. At Intermediate 2and Higher levels you are expected to learnthese prefixes off by heart. SQA plans tomake an example of this data sheet availableon its website prior to the exams.

Whether you are sitting Higher, Interme-diate 2 or Standard Grade, your notes forthis year should have been altered in schoolto take account of these changes. If you areusing older past papers or textbooks, or ifyou have someone else’s software or coursenotes from previous years, then you need toremember that the terms and definitionshave changed since these were published –for example, at time of writing, the SQAwebsite specimen Higher paper still hadquality factor in use rather than itsreplacement wR.

RESOURCES

Gather all your resources together – ideallyyou should have a wide range of materialsthat fit with your revision plan.

Firstly, get reading materials you can easilyaccess or dip into to check facts or remindyourself of something. This could besummaries you have completed or madeyourself, or commercial summaries youhave bought. You will also need to haveyour own Physics notes from school. Ifthese are handwritten or copied from afriend, make sure they are accurate copies.

If you are comfortable with a particulartextbook then obtain an up-to-date versionof it. This should have worked examplesand problems with solutions or answers foryou to check. Be careful with older text-books since course arrangements change –some books may have extra materials youdo not need, or even worse, might not coverall the content of a course. For Highers, arule of thumb would be to look for theMOSFET in a Higher book and a moderndate of publication in other texts if youwant to check suitability, although most NQHigher or Intermediate 2 textbooks willhave the latest SQA arrangements changesbuilt into them this year.

In a revision plan near the exam, themain use of your reading materials is tocheck the information you need to answerproblems that you are doing from yourassessment materials.

The main sources of the absolutely vitalassessment materials are outlined below.Extensive use of these these materials iscrucial to passing the exam.

Get a hold of official SQA Leckie & Leckiepast paper questions and solutions (theseare available from most bookstores). Youcan also download specimen papers freefrom the SQA website. Buy and usecommercially published, structured andrevision questions like those by CampbellRobertson in the P&N series and LynnRobinson in the Chemcord series.

You need your own school’s assessmentmaterials, especially examples of integrativequestions to try out – your school may havegiven you course questions which coverwork from different units. It’s importantthat you use these materials properly.

Higher candidates should try to get

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4 sundayherald 2 April 2006

PHYSICS

Resources designed to suit the way you study

hundreds of multi-choice questions (withanswers) to practise with. All studentsshould check their pace of work by allowingtime limits for questions; this also allowsyou to plan breaks.

If you are sitting Standard Grade, makesure you have materials for both Generaland Credit level. Sometimes pupils whoknow a lot can be sidetracked into writingtoo much in a General paper and can runout of time, so don’t forget to pace yourselfusing the marks allocations on thequestions to help you allocate your time.

Computer software and the internet flashlearning have excellent software thatcovers all Scottish S3 to S6 Physics atwww.jsharkey.oneuk.com.

Your school will need to hold a licencebefore you can buy student copies to use athome. It is worth asking what your schooldepartment has, because many will allowstudents access to computers and softwarefor planned and structured revisionbetween examinations. Other companies,such as Sure Q, also offer similar fairlyinexpensive packages for students’ home-use discs, so do check at school.

Standard Grade students can often getlots of help from packages designed forIntermediate 1 and Intermediate 2.

Some of you will have access to onlinesupport packages set up by your school orauthority. Higher and Advanced Higherstudents may have Scholar online accessfrom Heriot-Watt University. (If you do havethis then your school will have a passwordentry for you.) Sometimes a Google-typesearch can reveal resources on otherschool websites which can be of great helpto you.

This close to exams, you should beusing the internet as an alternative sourceof information or problems, or as some-thing to break your routine, not as yourmain study method. Get specimenpapers or do exercises online throughBBC Bitesize.

Specimen papers are available from theSQA online at www.sqa.org.uk.

At time of writing, Intermediate 1 and 2,Higher and Advanced Higher wereavailable to download or print. To accessthem, navigate through the “who are you?”window, choosing “pupil”, then throughthe “subject choice” window, choosing“Physics”.

Another good resource is BBC BitesizePhysics Scotland www.bbc.co.uk/scotland/education/. Click on “bitesize” and choosethe appropriate subject.

One or two schools have their ownspecific site; if your school has one, then itmight be appropriate to use it to save timesearching out the good from the bad.

Don’t forget that friends and family canbe a great resource. Sometimes it is a goodidea to work in a little group, but beware ofit degenerating into a chat session andsimply wasting time. However, havingtelephone numbers, e-mail or MSNaddresses can give you virtually instantsupport from friends when you need itmost.

If you are planning to use friends andrelatives or tutors outside school forextra help, then check that they will beavailable when you need them. Tutorsespecially will be in heavy demand up toTuesday evening of May 16. If networkingwith friends, set up rules about how late itis appropriate to call each other and forhow long.

You should take advantage of any extrasupported study, weekend or holiday classesoffered by your school, local colleges oruniversities.

STUDY TECHNIQUES

No matter which course you are taking, itmakes sense to lay out a study plan for yourrevision. Calculate realistically the numberof days you have left that you are going todevote to Physics. Then decide what tasksyou have to carry out and thus lay out acalendar with work planned for each day.Set short-term targets and include a varietyof tasks to keep your mind fresh. Stick toyour timetable as much as you can.

Focus on learning how to use equations,theory, and doing past papers and problemswhere you can check your answers withproper solutions.

There is a range of study techniques youcan use to help you learn Physics.

EQUATIONS, UNITS LISTS, MIND MAPSIn the Physics exams, you will be givenequations lists in a data booklet, but it helpsto learn equations off by heart because itimproves your pace of work.

You should go through your notes andsummaries and write down all the equationswith their units and a brief reminder noteabout when to use them.

You should then check where these arein your copy of the data booklet, so you canfind them easily during the exam if youhave a mental block.

If you prefer to use the triangle format forequations, then learn it in a form that putsthe left hand side of the equation at the topof the triangle.

Using Ohms law: In Standard Grade andIntermediate 2 courses, the basic equationis V = I x R, so in triangle format thiswould be:

All candidates need to gather tools of theexam trade. In your exam you may needthe items listed below. You will need topractise using some of them before the testand take all of them with you to theexternal examination.n A pen and spare pen that is comfortableto hold and use for most things you write.n A copy of the examination data booklet,which contains the formulae that you maywant to use during the examination.n A pencil for graphs, scale drawings,sketching ray paths and most diagrams.n A rubber for correction – don’t usecorrecting fluid, it takes too long to dry andtime is precious.n A 30cm ruler, which is transparent witha clear scale so you can measure and“curve fit” graphs and see the plottedpoints as you are setting up the ruler todraw the line.n A calculator of the type allowed in theexamination. Check this in school in advanceso you don’t have yours removed at the lastminute. Make sure you do not rely on asolar-powered calculator in case WednesdayMay 17, turns out to be a bright sunny day.If it is, curtains may be drawn during theexam and solar-powered calculators thatwere fine in winter or spring-light conditionsmay not work in the darker rooms or hallsused for the SQA exams.n No mobile phones will be allowed in casethey ring or people start texting orphotographing answers. If exam supervisorsfind people doing this sort of thing they willbe withdrawn from the examination.

At Higher Or Intermediate 2n A protractor or angle measurer for opticsor vector use and a watch or timer.

At Standard grade, your study plan shouldcover:n Telecommunicationsn Health Physicsn Understanding Electricityn Electronicsn Transportn Energyn Space Physics

For Higher grade, you should revise:n Mechanics and properties of mattern Kinematicsn Dynamicsn Electricityn Circuitsn AC theory and Capacitancen Analogue electronics

Don’t panic if you don’t have access to allof the exam tools listed, just gather whatyou have and use them properly. Usingresources properly means you need to layout a study plan which covers thefollowing Units:n Mechanics and properties of matter.n Kinematics and vectors, for example,equations of motion and projectiles.n Dynamics, for example, acceleration,forces, momentum and impulse.n Properties of matter, for example,density, pressure, the gas laws, kinetictheory of gases and uncertainties.n Electricity, including circuits, series andparallel equations, internal resistance,potential dividers and Wheatstonebridges.n AC theory and capacitance, peak andrms, voltage, frequency measurement,capacitor charge and discharge, ACtheory and capacitors, capacitorapplications.n Analogue electronics, ideal operationalamplifiers definitions, inverting circuitsapplications, gain equation, phaseinversion, square wave production,differential mode circuits andequations.n Radiation and matter, including wavetheory and wave optics, wave equation,interference theory, wave effects,diffraction and spectra, refraction andSnell’s law, critical angle and prismspectra, optoelectronics semiconductortheory, inverse square law, p-n junctiontheory, recombination energy, electronhole theory, the MOSFET, transistorswitches.n Fission, fusion, and dosimetry, E = mc2,inverse square law for gamma radiation,half-life, half-thickness, absorbed dose,dose equivalent, safe practice in usingradiation.

You need to practise integratedquestions involving information or ideasfrom more than one unit.

Learning And EquationsAt Higher you still need to focus veryheavily on learning and using the equations.You must learn theory and show you canreproduce it by working through pastpapers and problems from which you cancheck your answers with proper solutions.Make sure you are working fast enough andcan use the new data booklet properly.

Once you have your physics specificplan, stick to it as well as you can butremember you have to be a bit flexible inpractice, if something puts you offschedule do not give up, thousands ofpeople pass Higher Physics every year, socan you.

Don’t panic if you don’t have access to allof the exam tools listed, just gather whatyou have and use them properly. Nomatter which course you are sitting, itmakes sense to lay out a study plan.n Calculate realistically the number ofdays you have left that you are going todevote to Physics, decide what tasks youhave to carry out and lay out a calendarwith work planned for each day.n Set short-term targets. For example:Monday night, 1 hour. Read, and highlightan Electricity Unit Summary. Write downthe equations from the Unit and practiseone past paper problem involving eachequation.n Try to include a variety of tasks in yourplan, for example, draw a mind map forthe unit or list all the keywords in a pieceof theory.

During your revision of third year workyou will still be learning new materials, soyou need to keep a balance between oldand new work.

In a perfect world, your plan forrevision will include rereading summaries ofall the sections from telecommunicationsto space physics and learning off-by-heartall Physics equations, and the meaningof the symbols used in the equations, or at least becoming familiar with where the equations are laid out in the databooklet.

You would also want to memorise allphysics measurement units, such as, onelength in metres (m) and be able to useyour knowledge to check estimateanswers; for example, you should spot acar travelling at 300ms-1 is going too fastfor that to be a likely answer to aquestion.

Equally, a lamp drawing a current of3000 amps would be silly.

Make sure you focus your time veryheavily on learning how to use equations,theory, and doing past papers andproblems where you can check youranswers with proper solutions.

If you are stuck, find help from within your own organised resources orask advice from your teacher. If yourschool no longer has a Head of Physics,because of management restructuring,then find out who the faculty manager in charge of Physics is. She or he will beable to direct you to the resourcesavailable to you in your school or localauthority.

Once you have your Physics-specificplan, stick to it as well as you can butremember, all schedules have to be a bitflexible. If something puts you offschedule, don’t give up. Thousands of peoplepass Physics every year, so can you.

V

I x R

From previous pageEXAM TOOLS STANDARD GRADE TIPS HIGHER GRADE TIPS

WHAT TO REVISE

2 April 2006 sundayherald 5

PHYSICS

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To use the triangle, you cover the symbolyou want to find with your finger. To find R,for example, cover over the R on the triangle.You are left with V on top and I below, so theequation is R = V/I

Remember, you get no marks for simplywriting down the triangle. You must writedown the equation separately.

The good news for Intermediate 1students is that you should only have tolearn the equation one way round; you willnot normally be expected to rearrangeequations.

People who are visual thinkers oftenprefer to start with the triangle format.During revision, visual thinkers may benefitmost from using a concept map or mindmap (pictured right) as a summary learningtool or as a way to link ideas together.

WORK TO TIME LIMITS.At Standard Grade – as in all exams – whenyou do past papers you should timeyourself, both in revision and in the exam.

At Credit level there are 105 minutes for100 marks, which gives 63 seconds permark, so a 10-mark question at Credit levelshould take up 10.5 minutes.

At General level there are 90 minutes for80 marks, which gives 67.5 seconds permark, so an eight-mark question shouldtake 9 minutes.

Work it out for your own exam questionswhen you practise pacing yourself.

MNEMONICS AND MEMORY TRICKSMnemonics and memory tricks can benonsensical, as long as they help youremember the correct Physics.

ROYGBIV is familiar to many students asan easy way to remember the colours of thevisible spectrum – red, orange, yellow,green, blue, indigo and violet are thecolours in order from long wavelength toshort wavelength.

Using colour when writing informationor facts can also help you to memorisethem, as can chanting them.

STUDY TECHNIQUES FOR HIGHER GRADEUse the techniques you have developedalready when you studied for StandardGrade or Intermediate 2.

However, multiple choice questions aremuch more important than at Credit level,so you need to study lots of them. Therealso seem to be a higher proportion ofproblem-solving questions demandingcomplex descriptive answers, or multi-stage answers, so practise them. You willprobably have to allocate much morerevision time for Higher than you did forStandard Grade.

STANDARD GRADE EXAMS

First remind yourself that the exam can bepassed. Last year, 16,917 students satStandard Grade Physics: 58.2% passed atCredit level and a further 31.5% achieved aGeneral level pass.

The actual pass mark at each grade was:

Credit KU out of 50 General KU out of 40Grade one: 30 Grade three: 17Grade two: 21 Grade four: 10

Credit PS out of 50 General PS out of 40Grade one: 33 Grade three: 22Grade two: 22 Grade four: 19

So if your exam in May is about the samelevel of difficulty as last year, then you cansee what marks you need to aim for in eachgrade as a minimum. Last year’s Knowledge

pass marks were at a lower level than normalbecause of the difficulty of the exam.

TIPS FOR THE EXAMn The first and most obvious rule is turn upon time for the exam.n Do all the paper, or as much of it as youcan in the time.n Try to check every answer, if you havetime.n Never score out any answer until youhave written its replacement. You can circlethe wrong answer and write “ignore thisplease” if you want rid of something – thatway if you change your mind again all youhave to rub out is “ignore this please”.Never, never leave both answers – theexaminer will ignore both!n Use diagrams to help with your answers.You can reduce descriptive answersconsiderably with a neat, good-sizeddrawing. For example, at Standard Grade theanswer to a question on focussing rays by alens is much better drawn than described:

MISTAKES TO AVOIDEvery year candidates make mistakes thatcould be avoided. Here are some examplesof things to watch for.n Always put units in answers.n Think about the prefixes in questions orin your answers – mixing up milli ampswith Mega amps means the answer iswrong by a thousand million times. (If youuse a thousand million times too muchpower you might be roasted).n Lots of people used phrases such as “abigger resistor” when they meant “a biggerresistance”. This sort of mistake can be easilycorrected.

Turn to next page

V

I x R

MIND MAP

Energy lossesmean that

efficiency isalways less than

100%

Energy losses

Efficiency

%Eff =P outP in x 100

Heat energy canbe lost through

conduction,convenction,

radiation

Efficiency of a lift motor

%Eff =Potential energyElectrical energy

x 100

x 100

x 100=mgh

E out

ltv

%Eff = E in

6 sundayherald 2 April 2006

PHYSICS

Supporting students from Standard Grade to Advanced Higher

HIGHER GRADE EXAMS

Again, remember that the exam can bepassed – last year 83.2% of candidatesachieved an award from A to D.

In Higher Physics you have 150 minutesfor 90 marks, which is about one minuteand 40 seconds per mark. This means youshould take about 33-34 minutes to do 20multiple choice questions.

Students make similar mistakes everyyear, according to SQA principal examiners.Make sure you avoid these mistakes:n Forgetting direction in vector questions.n Using gravity as a label instead ofgravitational force or weight.n In internal resistance questions, forgettingthat changes in external resistance causechanges to current which also change“lost volts”.n Confusing the name of an object with thephysical quantity – for example, writing“increase the size of the resistor” instead of“increase the resistance”.n In optoelectronics, being unable todescribe how a laser works or how light isproduced in an LED.n Mixing up chemical reactions withnuclear reactions.n Do not use arrow symbols in descriptivequestions. In a gas laws question, for example,write “as the temperature increases, thekinetic energy increases”, rather than “asthe temperature > the kinetic energy >”n Forgetting basic definitions like emf.n Candidates should use SI units – 0.016seconds is the same as 0.016s, but it wouldbe incorrect to write as 0.016 secs.n Always put a zero at the origin of a graph,if appropriate to do so.n When two or more attempts have beenmade for the same part of a question,candidates must score through the partthey do not wish to be considered.

DRAWINGS AND DIAGRAMS

In Higher Physics, projectiles and vectorquestions can be made very much easierwith drawings helping to specify thedirections of movement or forces.

Question:

When two vectors are symmetrically posi-tioned (above), simply resolve each vectorin to the same direction – in this case thehorizontal component:

Vector A has a horizontal component =100 Cos 20 to the right and Vector B has ahorizontal component = 100 Cos 20 to theright so the resultant = 2 x 100 Cos 20o to theright = 187. 94 N to right

The most common calculation problemsare found in what teachers call thestandard 2-marker format

Question:Find the voltage across a four ohm resistorwhen a current of three amperes flowsthrough it.

Write the equation: V = I x R (1/2 mark).Substitute in the numbers for the thingsyou know: V = 3 x 4 (1/2 mark)Calculate the answer and write it down witha unit: V = 12 volts (1 mark) (Usually, a1/2 mark is deducted if there is no unit.)

This type of question can become a 3-markerif you have to take information from anothersource, such as a table in the data sheet.

Question:Calculate how long it takes for sound totravel 30cm through body tissue.

Write equation:Speed (v) = distance/timeSubstitute known numbers:v = 0.3m/t

At this stage it looks as we have twounknown variables, v and t. However, in thedata sheet the value of the speed of soundin body tissue would be found and shouldbe substituted into the equation for anextra mark, so: v = 1500 = 0.3/t and thereforet = 0.3/1500 = 2 x 10-4s

KEY WORDSLook out for words that are key tounderstanding how marks are allocated to aquestion.n Find usually means do a calculation towork something out numerically.n Describe means write down what youwould actually see or do.n Explain why means give an answerbased on Physics theory to clarify what ishappening. For example: Explain whymicrowaves are detected behind a metalbarrier. Expected answer: “The microwavesare diffracted round the barrier edge.”n Explain how usually means give practicalsteps in an experiment or process toillustrate what is happening. For example:Explain how microwaves are detectedbehind a metal barrier. Expected answer:“An aerial is placed behind the barrier andis used to detect the microwave signal.”n State means write down a statement or alist for the answer; no explanation isrequired.n Estimate means make an educated guessbased on reasonable interpretation ofinformation. Example: if asked to estimatethe time for a car to go a fixed distance intown, it would be reasonable to use timeswhich gave speeds less than the urbanspeed limit (about 13 ms-1) or close to thatvalue. If you estimated times in milliseconds that gave speeds of hundreds ofmetres per second – possibly faster thansound – that would be unreasonable.n Give two answers means give two, thereare no marks for extra ones – if you giveextra wrong answers they can sometimescancel out correct answers.n Highlighted words in bold or in italics areimportant.

LAYOUT OF ANSWERSAlways write as clearly and as neatly as youcan, it makes life easier for the marker andthey can give you all the marks you deserve.

Try to use directional words and phrases,such as increases, decreases, stays thesame, not vague words and phrases such aschanges, alters size and so on.

If you can use an equation to back up awritten answer do so, but do not use toomany significant figures in an answer.For example: 10/3 = 3.33 is reasonable;3.333333 would lose marks.

As a rule of thumb, look at the data in thequestion. If it is to three significant figures,you will probably lose marks for using threeor more figures too many, or two or morefigures too few, in your answer.

In Intermediate 1 and Standard GradeGeneral level, problems should have exactsolutions so you don’t have to worry aboutsignificant figures.

Also remember that spelling of somewords is important – diffraction and refrac-tion, fission and fusion, for example.

If you have a multi-stage descriptiveanswer to write, break it down into a set ofbullet points. Try to do this in a logicalorder, especially when explaining somethinglike the switching action of a transistor inelectronics:n Start by explaining how the input voltageschange with the input conditions.n Secondly, explain the changes or valuesof voltage needed to operate the switch.n Lastly, explain what happens at the outputof the system.

MULTIPLE CHOICE QUESTIONSn Practise lots of them and make sure youare getting them right by checking answerbanks for General level. You rarely findmultiple choice in the Credit level paper.Do every past paper multi-choice you can,sometimes similar questions reappear.n When puzzled, try to eliminate answersthat are clearly wrong. Often multi-choicecan be reduced to true or false by thismethod.n Read the first part of the question and tryto work out the solution before looking atthe responses.n Always include working out – you can dorough work on the question in the paperright beside the question. This makes itmuch easier to check if you have time.

HIGHER GRADE QUESTIONS

The most common calculation problemsare based on the standard 2-marker format– read the Standard Grade notes above formore information.

At Higher, you will need to consider thegreater likelihood of more complex, multi-stage questions. Sometimes you will haveto lay out your equations and data clearlybefore you know how to do the question.

Data sheets will be found in the Higherand Advanced Higher exams.

KEY POINTSn Look out for words that are key tounderstanding how marks are allocated to aquestion. See the Standard Grade notesabove for information.n Estimate means make an educated guessbased on reasonable interpretation ofinformation. These questions only havecorrect answers based on the estimateused.n You only get marks for equations atHigher if a substitution is made into themas part of the answer, or if the equationrepresents a principle, such as conservationof momentum.

LAYOUT OF ANSWERSYou will write the answers for this exam ina separate booklet, not on the answer paperitself. This makes it even more importantto always write clearly. Leave space betweenanswers so you can change them or addinformation later.

It is vital to clearly identify which question

(and which part of a multi-stage question)you are answering.

If you have a multi-stage descriptiveanswer to write, it can be a good idea tobreak it down into bullet points. Try to dothis in a logical order. For example, whenexplaining the pressure increase in a gas offixed mass and at constant volume:n Start by explaining how temperatureaffects kinetic energy of the particles andthe speed and motion of the particles.n Secondly, explain the effects of thesechanges or impulse per collision, force percollision and number of collisions persecond.n Next, explain how force and gas pressureare affected.

MULTIPLE CHOICE QUESTIONSAgain, practise lots of them and checkanswer banks. When stuck, try to eliminaterubbish – often multi-choice can be reducedto true or false by this method. Always readthe first part of the question and try to workout the solution before looking at theresponses. Put rough working in the paperbeside the question so you can check youranswers later if you have time.

If you run out of time in the multiplechoice, make educated guesses. Do notleave grid boxes empty.

You should consider the order you do thepaper in carefully. Some people suggestdoing the multi-choice Higher questionslast, after doing the written questions, butyou should always do what you feel mostcomfortable with.

When relationships in questions getcomplicated, use substitution methods –put numbers into equations and thenrearrange the numbers instead of theequation to see what happens.

In questions with graphs, when a graph isa straight line through the origin, whateveris on the upright axis is directly propor-tional to the variable on the horizontal axis.

INTERMEDIATE 2

Both the Standard Grade and Higher advicewill apply to your exam preparation.

In Intermediate 2 Physics, the specimenpaper shows 100 marks in 120 minutes,which is 1.2 minutes per mark or oneminute 12 seconds per mark, so a 5-markquestion should take six minutes maximumto answer.

From previous page

40 degrees

100N

100N

B

A

40 degrees20 degrees 200 cos 20 to right

100N

100N

B

A

PHYSICS EXAMTIMETABLELevel/Paper TimeWednesday May 17General 9am-10.30amCredit 10.50am-12.35pmIntermediate 1 1pm-2.30pmIntermediate 2 1pm-3pmHigher 1pm-3pmHigher 1pm-3.30pmAdvanced Higher 1pm-3.30pm

Exams below are on the same day asPhysics. Make sure you have madeproper arrangements with your schoolif you have two exams at the same timeScience, CreditScience, FoundationScience, GeneralEconomics Intermediate 1Economics Intermediate 2Economics HigherEconomics Advanced HigherMusic Higher Listening (Core)Music Higher Listening (Extension)Music Advanced Higher Listening (Core)

b b

2 April 2006 sundayherald 7

PHYSICS

Visit your local bookshop now for special offerson Official SQA Past Papers!

SEE ADVERT IN MAIN PAPER FOR DETAILS

STANDARD GRADEMaking questions relevant to the real worldallows situations unfamiliar to students to beused. The application considered in thefollowing question would at best have beencovered in an internet search or video byStandard Grade Physics students. Moststudents would be unfamiliar with the contextin which familiar theory is being applied.

However, questions like this reflect the bodyof knowledge our future medics and medicalengineering graduates will need to know.

QuestionA radioactive tracer is injected into a patientto investigate the rate at which blood flowsin the veins of the legs. The tracer is injectedinto veins in the feet, and detectors areplaced beside both ankles and knees of eachleg as shown in the diagram.

The graphs show how the count rates at thedetectors vary for each leg.

(a) The graph obtained for the left legindicates that the blood flow in that leg isnormal. How long does it take blood to travelfrom the ankle to the knee in the left leg?AnswerEight seconds (taken from graph!)

(b) Explain why the graph obtained for theright leg indicates that there could be ablockage in a vein in the right leg.AnswerThe count rate shown in the graph remainshigh in the right ankle showing that theblood had not flowed very quickly to the knee.OR The count rate in the knee is not highenough showing not enough blood hadflowed to the knee.

(c) The hospital keeps three radioactiveisotopes for different uses. These are shownin the table below.

Isotope Half-life RadiationNa-24 15.1 hours gammaY-86 14.7 hours betaTc-96 4.3 days gamma

(d)(i) Which isotope should be selected for theblood flow investigation?Answer Na –24 should be chosen because its gammarays will penetrate the body to reach thedetectors outside the legs and because it has areasonably short half life so the patient willnot remain radioactive for long.(d)(ii) Why are each of the other two isotopesnot suitable?AnswerIsotope: The Y-86 is a beta source and betaparticles will be absorbed by the body and willnot reach the detectors.Isotope: The Tc-96 has a half life of 4.3 daysso the person will remain radioactive forseveral days after the procedure is completed.

(e) The patient could also be given an injectionof another isotope Au-79 with an activity of10kBq. This isotope has a half life of 2.7 days.The patient must be kept under observationuntil the activity falls to 1.25kBq.

Calculate how long this will take.AnswerThe answer is found by halving the activityuntil it reaches the specified level andtherefore finding the number of half lives andtotal time. A table like the one below is oftenthe preferred layout for working.

Activity Number of Number ofat start half lives days passed10kBq 0 05kBq 1 2.72.5kBq 2 2.7 + 2.7 = 5.4

(b) Describe how the spot at the centre of thescreen produced by the electrons can bemoved to position X. Your answer must makereference to the relative sizes and polarity (signs)of the voltages applied to plates P and Q.

AnswerTo move the electron beam upwards by one gridsquare apply a positive voltage V to plate P.

To move the beam to the right two gridsquares apply a positive voltage of 2V toplate Q.

This Higher question might be regarded asdifficult because the basic physics in thequestion is set in an unfamiliar context formost students. Not many Higher candidateswill have been in space or be old enough toremember much of the televised material fromearlier space exploration. Students taking partin the Scottish Space School modules runjointly by Nasa and Scottish Enterprise(organised by Careers Scotland) might beexceptions to this unfamiliarity with space.

QuestionA space vehicle of mass 2500kg is movingwith a constant speed of 0.50ms-1 in thedirection shown. It is about to dock with aspace probe of mass 1500kg which is movingwith a constant speed in the opposite direction.

After docking, the space vehicle and spaceprobe move off together at 0.20ms-1 in theoriginal direction in which the space vehiclewas moving

(a) Calculate the speed of the space probe justbefore it docked with the space vehicle.AnswerThis is a conservation of momentum question.We solve it by using the fact that totalmomentum before and after the collision arethe same when no external force is acting.

Momentum before is the vector momentumof the probe and vehicle added together.

So we write a suitable equation andsubstitute values into it, as shown below.

momentum before = (m x v)vehicle + (m x v)probemomentum before = momentum after momentum after = (mp + mv) x v (the masses are added because the spaceprobe and space vehicle stick together afterthe collision)

So, writing the equation for conservation ofmomentum:(m x v)vehicle + (m x v)probe = (mp + mv) x v

We then substitute the data into the equations:(2500 x 0.5) + (1500 x v) = (2500 + 1500) x 0.2So 1250 + (1500 x v ) = 4000 x 0.2 = 800 So 1250 - 800 + (1500 x v ) = 0So 450 = -1500 x v and v = 450/-1500 = -0.3 ms–1 where thenegative sign tells us that the direction of thespace probe was opposite to the direction ofthe vehicle.

HIGHER GRADEHere is an example of a Higher Grade Integrativequestion. These are regarded as more difficultbecause these questions combine ideas fromdifferent units. If you are serious about gainingan A then you will need to answer some of thesequestions correctly to gain enough marks.

Higher Physics 1998 QuestionThe diagram below shows a cathode ray tubeused in an oscilloscope.

The electrons which are emitted from thecathode start from rest and reach the anodewith a speed of 4.2 x 107 ms-1

(a)(i) Calculate the kinetic energy in joules ofeach electron just before it reaches the anode.AnswerThe kinetic energy is found using the equationEk = I/2 mv2 – where m is the mass of theelectron found in the data sheet at the start ofthe examination and v is the velocity of theelectron reaching the anode.Ek = 0.5 x 9.11 x 10–31 x (4.2 x 107)2

= 8.04 x 10–16 J

(b)(ii) Calculate the pd between the anodeand the cathode.AnswerThe change in kinetic energy 8.04 x 10–15J isequal to the electrical energy Ee gained by theelectron so we can use the equationEk = Ee = q x V where q is the charge on theelectron and V is the required pd.

8.04 x 10–16J = 1.6 x 10–19 x V so that V = 8.04 x 10–16J / 1.6 x 10–19

= 5.03 kV

Detectors

Detectors

0 2 4 8 10 12

300

Left Leg

ankle

Time from injection in s

Count ratein counts

per secondknee

0 2 4 8 10 12

300

Right Leg

ankle

knee

Time from injection in s

Count ratein counts

per second

WORKED EXAMPLES

(b) The space vehicle has a rocket enginewhich produces a constant thrust of 1000N.The space probe has a rocket engine whichproduces a constant thrust of 500N.

The space vehicle and space probe arenow brought to rest from their combinedspeed of 0.20ms–1.

(b)(i) Which rocket engine was switched onto bring the vehicle and probe to rest?AnswerThe space probe engine was switched on(since it exerted a thrust opposite in directionto the motion of the two space ships).

(b)(ii) Calculate the time for which thisrocket engine was switched on. You mayassume that a negligible mass of fuel wasused during this time.AnswerOne way to solve this question is find theacceleration of the pair of spaceships usingF = m x a then use v = u + at to find the time.

We need to remember that theaccelerating force acts opposite to thevelocity and therefore acceleration has anegative sign compared to the velocity.

So the magnitude ofF/m = 500/4000 = 0.125 ms-2

and the acceleration is -0.125ms-2

substituting into v = u + at we get 0 = 0.2 + (-0.125t)0 = 0.2 + (-0.125t)So -0.2 = -0.125tSo t = 0.2/0.125 = 1.6 seconds to come to rest

Another way is to assume the rocket enginesapply an impulse to the spacecraft to changetheir momentum.

Change in momentum = average force x timefor force to act

So, 4000 x 0.2 = 500 x t

and (4000 x 0.2) = t 500

so t = 800/500 = 1.6 seconds

(c) The space vehicle and space probe are tobe moved from their stationary position at Aand brought to rest at position B, as shown.

Explain clearly how the rocket engines ofthe space vehicle and the space probe areused to complete this manoeuvre. Yourexplanation must include an indication of therelative time for which each rocket enginemust be fired.

You may assume that a negligible mass offuel is used during this manoeuvre.Answer The engines of the space vehicle which exerta thrust (force) of 1000N would be switchedon for a set time which would accelerate thevehicles towards B, then switched off. Withthe engines off, the vehicles would then movewith constant velocity towards B since nounbalanced force would be acting on them.

In order to decelerate the vehicles back torest at B the space probe engines wouldhave to exert a decelerating force. Theywould have to switched on for twice as longas the original “burn” of the space vehicleengines since they only exert half the thrustof them.

cathode

heater

anodeP

Q

screen

space vehicle0.50ms-1

spaceprobe

space vehicle and space probe0.20ms-1

A B