Individual Study Plan: Unit 1 Materials

Subject:PhysicsTeacher:N.Lad

Student:UnitUnit 1

Study Task outline:Materials ISPThis ISP covers the Materials part of Physics Unit 1: Physics on the Go. While much of the topic contains mathematical concepts which you will be asked quantitatively (using numbers) you may be asked to explain these ideas qualitatively (using words). This ISP will help you build the skills required to answer both styles of questions and aid you to build your knowledge for your assessments.

It is of imperative importance that you can answer both quantitative and qualitative Physics questions; without this skill you will struggle to do any better than a D grade. To achieve a grade A-C you will need to be able to bring together different areas of Physics you have learnt (e.g. terminal velocity and distance/velocity time graph). You must also be able to use an equation in a qualitative manner, explaining the implications of changing a variable in the equation. The specification points in this ISP are all of the specification points within the Materials module (see your introduction to AS Physics booklet).

The A* grade is awarded if the candidate meets two requirements: Grade A for the overall Advanced GCE 90% of the total available uniform marks for the A2 unitsThis means that you can get a B grade in AS Physics and still achieve an A*in A2 PhysicsA* students should be able to: apply principles and concepts in familiar and new contexts involving only a few steps in the argument describe significant trends and patterns shown by data presented in tabular or graphical form and interpret phenomena with few errors and present arguments and evaluations clearly explain and interpret phenomena with few errors and present arguments and evaluations clearly carry out structured calculations with few errors and demonstrate good understanding of the underlying relationships between physical quantities.

Exam questions where you are asked to describe experiments are often worth 6 marks, which can help you reach the next grade up of an exam paper. In these questions you need to:Clearly state the equipment required, explain and justify the equipment you have chosen, the measurement you make, and calculations you will do and also how you will make the experiment reliable to satisfy the criteria for full marks.

Past papers and other examboard information is available on the following website: http://www.edexcel.com/quals/gce/gce08/physics/Pages/default.aspx

TaskTask detailResources neededCompleted/comments

1Specification points covered : 18,19, 20, 21You should read through the notes from lessons and p50-62 from the course textbook. The areas to focus on are:1. The link between density mass and volume2. The physics of flow3. How the forces acting on an object change as it reaches terminal velocity (including stokes law)Complete Explaining Everything 1Complete questions 1 to 4 from your Materials ISP booklet and mark them.A-A* - how does flow link to air resistance? AS Physics Text book/Revision Guide

Explaining Everything number 1

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2Specification points covered : 22, 23, 23, 27You should read through the notes from lessons and p62-64 from the course textbook. The areas to focus on are:1. Hookes Law graphs2. Hookes Law experiments3. How to calculate the Elastic strain energy from a Hookes law experiment

Complete Explaining Everything 2Complete questions 5 and 6 from your Materials ISP booklet and mark them.A-A* - how does Hookes law link to the conservation of energy?AS Physics Text book/Revision Guide

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3Specification points covered : 24, 25You should read through the notes from lessons and p65-69 from the course textbook. The areas to focus on are:1. The shape of stress strain graphs2. How to calculate the Youngs modulus of a materialComplete Explaining Everything 3Complete questions 7 to 10 from your Materials ISP booklet and mark them.A-A* - how does stress and strain link to the work on equilibrium?AS Physics Text book/Revision Guide

Explaining Everything number 3

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4Specification points covered : 26You should read through the notes from lessons and p68-73 from the course textbook. The areas to focus on are:1. The definitions of terms that can be used to describe the properties of materials: brittle, ductile, hard, malleable, stiff, and tough. Complete Explaining Everything 4Complete questions 11 to 13 from your Materials ISP booklet and mark them.AS Physics Text book/Revision GuideExplaining Everything number 4

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5By now we have completed all the work required from Unit 1 Materials. Using your class notes complete the following tasks:Complete questions 14 to 17 from your Materials ISP booklet and mark them. A-A* - Make a list of area that link together from the materials and mechanics module (e.g. terminal velocity links with forces). Try and explain how the areas are linked.AS Physics Text book/Revision Guide

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Q - Questions completedE - Explaining everything completedM - Questions markedWWW want went wellEBI even better ifMRI My response is (student response)Explaining everything Task 1Define the following terms using diagrams where appropriate: density, laminar flow, streamline flow, terminal velocity, turbulent flow, upthrust and viscous drag.

Describe Stokes law and Archimedes principle. Show how the two can be interlinkedInclude the terms: viscosityterminal velocityupthrustweight

Explaining Everything Task 2State Hookes law and describe a Hookes law experiment. Describe how to find out the elastic strain energy.Include the terms: force extensionstringspringlengthstiffnessarea under

Explaining Everything Task 3Draw a stress strain graph and label the following points: limit of proportionality, elastic limit and yield point. Include a definition of each.

Explain the difference between elastic and plastic deformation. Include graphs to help.

Explaining Everything Task 4Explain the meaning of the following terms: calculate tensile/compressive stress, tensile/compressive strain, strength, breaking stress, stiffness and Young Modulus.

Define the following terms: brittle, ductile, hard, malleable, stiff, and tough. Give examples of materials with these properties.

Wootton Upper SchoolISP - Materials BookletTask 11.The velocity of a ball bearing falling from rest through syrup .......... with distance fallenAdecreases linearly from zeroBincreases from zero to a maximumCincreases linearly from zeroDstays constant at a non-zero value(Total 1 mark)

2.The process of turbulence was described in verse by the British meteorologist, Lewis F. Richardson:Big whorls have little whorls,Which feed on their velocity,And little whorls have lesser whorls,And so on to viscosity.Suggest what the author means by the word whorl.(1) Draw diagrams in the boxes below to show laminar and turbulent flow.Describe these flow patterns.Laminar flow

Description:(2) Turbulent flow

Description:(2) Turbulence can be used to reduce the rate of flow of a fluid.Explain this statement in terms of energy transfers.(2)(Total 7 marks)3.After wine has been fermenting it contains many small particles. These particles are allowed to settle so that they can be separated from the liquid.Add labelled arrows to this diagram showing the other two forces on a particle falling downwards within the wine.

(2)

The upthrust can be calculated using the expression where w is the density of wine and r is the radius of the falling particle.Explain how the above expression for upthrust is derived..............................................................................................................................................................................................................................................................................................................................................................................................................................................(2)Write down the equation relating the three forces acting on the particle when it reaches terminal velocity................................................................................................................................................(1)Show that the terminal velocity v of a particle of density s is given by the following expression:

where is the viscosity of the wine.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)Explain how you would expect the velocity of this particle to change if the temperature of the wine was increased..............................................................................................................................................................................................................................................................................................................................................................................................................................................(2)Stokess law is valid only provided the flow is laminar. Using a diagram, explain what is meant by the term laminar flow.

.............................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(Total 11 marks)

4.Some people think that all raindrops fall at the same speed; others think that their speed dependson their size.Calculate the speed of a raindrop after it has fallen freely from rest for 0.2 s...............................................................................................................................................................................................................................................................................................Speed = .(1) The raindrop falls for longer than 0.2 s. Explain why its acceleration does not remain uniform for the whole of its fall.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2) Show that the mass of a 0.5 mm diameter spherical raindrop is less than 1 107 kg.1.0 m3 of water has a mass of 1.0 103 kg...........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)Calculate the raindrops terminal velocity. Assume that the upthrust from the air is negligible. Explain your working clearly.Viscosity of air = 1.8 105 kg m1 s1............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................Terminal velocity = (3) Sketch a graph to show how the raindrops velocity increases from rest to terminal velocity. Add a scale to the velocity axis.

(3) Explain how the terminal velocity would be different for a larger raindrop.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(1)(Total 12 marks)

Task 25.A student carries out an experiment to investigate the extension x of a clamped copper wire when he applies a varying force F to the free end.

(a)The graph below shows his results.

(i)Add a line of best fit to the graph.(1)(ii)Add an X to the line to mark the limit of proportionality.(1) (b)(i)Calculate the energy stored in the copper wire due to a 20 N load..................................................................................................................................................................................................................................................................................................................................................................................Energy stored = ...........................................(3) (ii)What property of the wire could be determined by calculating the gradient of this graph?...........................................................................................................................(1) (c)Explain how the graph would be different if the student had used a thicker piece of copper wire................................................................................................................................................................................................................................................................................................................................................................................................................(2)(Total 8 marks)6.It is common for pens to have retractable ink refills. When a force F is applied to the button at the end of the pen, the tip of the refill is pushed out of the body of the pen. This compresses a spring in the end of the pen so that if the button is pressed again the refill is pushed back inside the pen.

(a)What sort of deformation must the spring undergo when compressed? Justify your answer................................................................................................................................................................................................................................................................................................................................................................................................................(2)In an experiment, an increasing force was used to compress this spring. The table shows the compression for each value of force.Force / NCompression / mm

0.00.0

1.01.9

2.03.8

3.05.6

4.07.5

5.09.4

6.011.3

7.013.1

8.015.0

(b)On the grid below, plot a graph of compression against force for this spring. Add a line of best fit to your points.

(3) (c)Calculate the stiffness of this spring...........................................................................................................................................................................................................................................................................Stiffness = ................................................(2)(d)In the pen, the spring is compressed by 6.0 mm. What force is needed for this compression?.....................................................................................................................................Force = ...................................................(1)(e)Calculate the elastic energy stored in the spring when its compression is 6.0 mm...................................................................................................................................................................................................................................................................................................................................................................................................................Elastic energy = ...................................................(3)(f)The spring is replaced by another with double the length but identical in all other ways. How would the force needed to compress this new spring by 6.0 mm compare with the force needed for the original spring?............................................................................................................................................................................................................................................................................(1)(Total 12 marks)Task 37.A force-extension graph for a long thin copper wire is drawn below.

Show clearly on the graph the region where the copper wire obeys Hookes law.What additional information would be needed in order to calculate the Young modulus for copper from this graph?...............................................................................................................................................Estimate the energy stored in the wire when it has been extended by 20 mm.Energy stored = ...(Total 5 marks)8.(i)A wire fence is made of steel wire of diameter 2.5 mm.Show that this wire has a cross-sectional area of approximately 5 106 m2................................................................................................................................................................................................................................................................................................................................................................................................................(2)(ii)A force of 1500 N is applied to tension a single length of this wire.Calculate the stress produced in the wire.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(iii)Hence calculate the extension, in mm, produced in a 33 m length of this wire when it is tensioned. The Young modulus of steel is 210 GPa.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(4)(Total 8 marks)9.The picture shows an Anglo-Saxon gold shoulder clasp excavated in 1939 from the Sutton Hoo ship burial.

The decoration of the clasp is known as cloisonn. The clasp was made by: Hammering gold sheet to the desired shape Fixing thin gold wires to the surface to make cloisons (compartments) Filling these cloisons or compartments with an enamel paste Heating to bind the paste to the gold, forming a hard, shiny, attractive layer.Gold was used to make this clasp because it has suitable properties. Fill in the gaps in the sentences to name the two properties described below.Gold can be hammered to form the basic shape. It is ..................................................Gold can be made into thin wires. It is ..................................................(2)

When gold wire is stretched, its load-extension graph would have the typical shape shown below.

The graph can be divided into two regions, A and B. Name the property exhibited in region A................................................................................................................................................(1)Explain what is meant by the terms hard and plastic behaviour.Hard..............................................................................................................................................................................................................................................................................................Plastic behaviour..............................................................................................................................................................................................................................................................................................(2)(Total 5 marks)10.Draw a labelled diagram of the apparatus you could use in a school laboratory to determine the Young modulus of copper in the form of a wire.

(3)Suggest an appropriate length for the wire being tested................................................................................................................................................

How would you determine the cross-sectional area of the wire?............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(3)State the unit of k, the constant of proportionality in Hookes law................................................................................................................................................(1)Show that for a wire of length l and cross-sectional area A the Young modulusE = kl/A..............................................................................................................................................................................................................................................................................................................................................................................................................................................(3)(Total 10 marks)Task 411.Complete the gaps in the following paragraph by selecting appropriate words from the following list.compressivedensityenergyforcemassstifftensiletoughIncreasingly, drinks containers are made out of polymers rather than glass. A containermade from a polymer such as polythene has several advantages over a glass container.Polythene has low ..........................................., and so the ........................................... ofthe container is kept low. Polythene is also ........................................... and so canabsorb a large amount of ........................................... before breaking. Glass isonly strong under ........................................... forces but polythene is also strongunder ........................................... forces.(Total 3 marks)12.The body armour worn by modern police officers falls into two categories: hard and soft.(a)Hard body armour gives more protection but is heavier to wear and does not give any flexibility of movement.(i)Circle the word which describes the type of behaviour hard body armour is likely to demonstrate.DuctileElasticPlasticToughState what is meant by the word you have circled....................................................................................................................................................................................................................................................... (2)(ii)Hard body armour is made of rigid ceramic plates. Ceramic materials are often described as being brittle. Why would this not be a desirable property for body armour?...........................................................................................................................(1)(iii)Many ceramics are not brittle, including alumina, the ceramic material used in body armour. Alumina is also a very strong material. What is meant by a strong material?...........................................................................................................................(1) (b)Soft body armour allows much greater flexibility of movement. Most soft body armour is made from Kevlar. A new fibre called Biosteel is now being developed, however, that is several times stronger than Kevlar.The manufacturers claim that Biosteel can be up to 20 times stronger than an ordinary steel wire of the same thickness.MaterialYoung ModulusBreaking strain

Steel2 1011 Pa0.1%

(i)Calculate the maximum breaking stress that steel can withstand.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................Maximum stress = ....................................................(2)(ii)Hence show that the force needed to break a steel wire of diameter 1 mm is about 160 N.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(3)(iii)If the manufacturers of Biosteel are correct, what maximum force would be needed to break a Biosteel fibre of the same dimensions as the steel wire?...........................................................................................................................Maximum force = ....................................................(1)(iv)State one assumption you have made in your previous calculations.......................................................................................................................................................................................................................................................(1)(Total 11 marks)13.Speed cyclists need to reach very high speeds when competing.

What word describes the preferred airflow around the body of a speed cyclist?...............................................................................................................................................(1)Draw the possible airflow above and behind the body of a speed cyclist

(i) in racing position(ii) when sitting upright.(2)What is the advantage to speed cyclists of travelling very close together as shown in the photograph?..............................................................................................................................................................................................................................................................................................(1)Would plastic or elastic better describe the material of the bodysuit worn by a speed cyclist?...............................................................................................................................................Explain your choice.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)

Would brittle or tough better describe the material of the helmet worn by a speed cyclist?...............................................................................................................................................Explain your choice.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)Explain why such a helmet is designed to deform in a crash...............................................................................................................................................................................................................................................................................................(1)(Total 9 marks)Task 514.The graph shows how a sample of material behaves when extended by a force.

(a)What does point B represent?.....................................................................................................................................(1)(b)State the physical property represented by the gradient of the section AB of the graph......................................................................................................................................(1)(c)Explain the significance of the area underneath the line from A to C...........................................................................................................................................................................................................................................................................(2)(Total 4 marks)

15.A skydiver accelerates towards the ground at 9.81 m s2 at the instant that he leaves the aeroplane.(a)Explain why his acceleration will decrease as he continues to fall.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(b)The skydiver opens his parachute. Explain why he reaches a terminal velocity shortly afterwards................................................................................................................................................................................................................................................................................................................................................................................................................ (2) (c)The velocity at which he then hits the ground is similar to that achieved when falling freely from a height of 3 m. Calculate this velocity.

Velocity = ................................(2)(Total 6 marks)16.A sign at a railway station advises passengers to keep back from the platform edge. This is because passing trains may cause turbulence.Explain what is meant by turbulent flow, and suggest why it is dangerous for passengers to stand near the edge of the platform..........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(Total 3 marks)

17.A raindrop has a radius of 0.70 mm. It is falling at terminal velocity through air.(a)Show that the mass of the raindrop is approximately 1 106 kg.Density of water = 1000 kg m3................................................................................................................................................................................................................................................................................................................................................................................................................(2)(b)Ignoring any upthrust on the raindrop, calculate its terminal velocity.Viscosity of air = 8.90 104 kg m1 s1.

Terminal velocity = ..................................................(2)(Total 4 marks)

18.List of data, formulae and relationshipsDataAcceleration of free fallg = 9.81 m s2(close to Earths surface)Boltzmann constant k = 1.38 1023 J K1Coulombs law constantk = 1/4 = 8.99 109 N m2 C2Electron chargee = 1.60 1019- CElectron massme = 9.11 1031 kgElectronvolt1 eV = 1.60 1019 JGravitational constantG = 6.67 1011 N m2 kg2Gravitational field strengthg = 9.81 N kg1(close to Earths surface)Permittivity of free space= 8.85 1012 F m1Planck constant h = 6.63 1034 J sProton massmp = 1.67 1027 kgSpeed of light in a vacuumc = 3.00 108 m s1Stefan Boltzmann constant5.67 108 W m2 K4Unified atomic mass unitu = 1.66 1027 kg19.MechanicsKinematic equations of motionv = u + ats = ut + at2v2 = u2 + 2asForcesF = mag = F/mW = mgWork and energyW = FsEk = mv2Egrav = mghMaterialsStokes lawF = 6rvHookes lawF = kxDensity = m/VPressurep = F/AYoungs modulusE = / whereStress = F/AStrain = x/xElastic strain energyEel = Fx

1.B[1]2.Meaning of whorl:An eddy/circular flow/whirlpool OEP (1)1Diagram and description of flow patterns:LaminarAt least 3 reasonably parallel and straight lines (1)No abrupt change in direction/no whorls/eddies (1)2Turbulent flowNo order shown in the flow/small broken circular shapes or similar (1)Mixing between layers of liquid/whorls/whirlpools/eddies occur along the flow (1)2Explanation of statement in terms of energy transfers:Kinetic energy, of motion of eddies becomes kinetic energy ofmolecules in liquid; overall kinetic energy reduces and flowslows/ordered kinetic energy disordered kinetic energy (1) (1)2[7]3.Add forces to diagramDownward arrow labelled weight / mg (1)Upward arrow labelled (viscous) drag (1)2Expression for upthrustUpthrust = weight of displaced fluid (1)= volume density g (1)2 Relationship between forcesUpthrust + (viscous) drag = weight OR F + U = W (1)1[ecf. From diagram must be 3 forces]Expression for velocityF = W U6 rv = 4/3r3 sg 4/3 r3wg (ecf) (1)6rv = 4/3 r3g (ps pw)v = (1)2Velocity change with temperatureVelocity will increase (1)As viscosity will decrease with temperature/as velocity increases with decreasing viscosity / as density of wine decreases (1)2Explanation of what is meant by laminarDiagram showing at least 3 reasonably parallel and straight lines (1)No abrupt change in direction/no whorls/no eddies (1)2[Both marks may be awarded from the diagram.][11]

4.Speed of raindrop: = u + at = 0 + 9.81 m s2 0.2 s = 1.96 m s1 2 m s1 (1)1Explanation:Air resistance (1)Drag force increases with (speed) (1)So resulting accelerating force/acceleration drops (1)Terminal velocity when weight = resistance (+ upthrust) (1)Max 2Mass of raindrop:Mass = volume densitysubstitute 1.0 10 3 kg 3 4 (0.25 103 m)3 /3 (1)6.5 108 (kg) (1)2 Terminal velocity:Viscous drag = weight (1)VT = (6.54 108 kg 9.81 m s2) / (6 1.8 105 kg m1 s1 2.5 10 4 m) (1)[Allow e.c.f. for m and r]So terminal velocity = 7.56 m s1 (1)3Graph:Line drawn which begins straight from (0,0) (1)Then curves correctly (1)to horizontal (1)Scale on velocity axis (1)[More than 2 sensible values and unit]Max 3Explanation:VT increases (because of greater mass) (1)1[12]5.(a)Graph:(i)Line of best fit completed curving between 5.0 and 5.5 mm (1)(ii)X marked correctly on line (by eye) between 5.0 5.5 mm (1)2(b)(i)Energy stored calculation:Energy = Fx or area under graph to intercept line (1)Correct reading of x from graph (1)Correct answer from graph in Joules (1)3eg.Energy = Fx= 20 4 103= 0.04 J(ii)Gradient of graph:Stiffness of wire (1)1 (c)Thicker wire:Any 2 of the following:Steeper gradientMore force required to produce the same extensionLimit of proportionality at a larger force (1)(1)Max 2[8]

6.(a)Deformation of spring:As spring must return to original length when (compressive) forceis removed (1)Elastic (conditional on 1st mark) (1)2 (b)Graph:4 points plotted correctly (1)all points plotted correctly (to within +/ square) (1)straight line of best fit through points and origin (1)3(c)Stiffness:Use of stiffness = F/x taking any pair of values from the table orgraph (1)= 0.53 N mm1 (530 Nm1) [allow 0.52 0.54 N mm1] (1)2(d)Force exerted:Correct reading from graph= 3.2 N [allow 3.1 3.3 N] (1)ORF = kx = 0.53 6 = 3.2 N [allow ecf] (1)1(e)Elastic energy:Energy stored = area under graph OR Energy stored = Fx OREnergy stored = kx2 (1)Correct values substituted [ignore powers of 10] (1)Correct answer (9.6 103 J) [allow 9.3 9.9 103 J] (1)3Example:Energy stored = (3.2 6 103) = 9.6 103 JOREnergy stored = 530 (6 103)2 = 9.6 103 J(f)New force to compress:Half of the original force / 1.6 N [allow ecf] (1)1[12]7.Region on graph where copper wire obeys Hookes law:Hookes law region up to (9,15)Additional information needed:Length and cross-sectional areaEstimate of energy stored in wire:Sensible attempt at area up to 20 mmAnswer in range 250 2700.26 J[5]8.(i)Fence wire cross-sectionUse of r2 and 103 m (1)4.9 106 (m2) [do not accept m] (1)A= r2= (0.5 2.50 103)22

(ii)Stress calculationSubstitution: 1500 N / 4.9 [or 5] 106 m2 (1)310 MPa [accept 300, ecf] (1)= F / A= 1500 N / 4.9 106 m2= 3.1 108 Pa2 (iii)Extension calculationE = / and = l / l (or E = F l / A l) (1)Substitution in E = / and = l / l [or in E = F l / A l, ecf,ignore 10n] (1)0.048 (m) [ecf] (1)48 mm [accept 47 49 mm, bald answer scores 4/4] (1)E= F l / A ll= (1500 N 33 m) / (210 109 Pa 4.9 106 m2)= 0.048 m = 48 mm4[8]9.Properties of goldMalleable (1)Ductile (1)2E.g. elastic, stiff1DefinitionsHard: material not readily scratched/indented (1)Plastic behaviour: material remains in stretched/deformed shape when force removed (1)2[5]10.Diagram of apparatus to determine Young modulus of copperWere firmly fixed to ceiling/beam/end of bench (1)Load and ruler/scale (1)Means of reading small extensions e.g. pointer againstscale/vernier (1)3Length of wire being testedAppropriate length 2 m [Less if vernier used] (1)Cross-sectional area of wireMicrometer (1)Diameter in several places (1)3Unit of k in Hookes lawN m 1/kg, s 2 (1)1 Show thatE = F/A e / l (1)= Fl/Ae (1)but F/e = k/substitute F = ke (1)3[10]

11.density, mass (1)

tough, energy (1)

compressive, tensile (1)

[3]12.(a)(i)Type of behaviour:PlasticCorrect definition of circled word:Ductile: can be pulled into a long thin shapeElastic: returns to original shape/size (once force removed)Plastic: does not return to original shape/size (once force removed)Tough: can withstand dynamic loads / shocks / impacts / absorbsa lot of energy before breaking2(ii)Brittle:Snaps / cracks / shatters / breaks without (plastic) deformation(when subjected to a force)1(iii)Strong:Large force / stress required to break it1 (b)(i)Breaking stress:Use of = ECorrect answer [2 108 Pa]Eg. = 2 1011 0.001= 2 108 Pa2(ii)Force to break wire:Use of A = r2Use of F = ACorrect answer [157 (N)][allow 156 157 (N) for rounding errors no u.e]Eg.A = (1 103/2)2 = 7.9 107 m2F = 2 108 7.9 107 m2Weight (= F) = 157 N3(iii)Force to break Biosteel fibre:3.1 103 N [allow 3.1 103 N 3.2 103 N]eg.20 157 = 3140 N (3200 N if 160 N used)1(iv)Assumption:Elastic limit (of both materials) not reached / elastic behaviour /Hookes law obeyed / Young modulus still holds at breaking point/ Area remains constant / best Biosteel scenario / 20 stronger1[11]13.Preferred airflowStreamlined/laminar flow (1)1DiagramsAt least one continuous curve drawn above body of cyclist (1)Turbulence shown behind cyclist (1)2

AdvantageLess drag on cyclist behind (1)OR airflow above bodies more streamlinedOR less work needs to be done by following cyclists Material of bodysuit and explanationElastic (1)e.g. stretch around body in use/nothing loose to cause turbulent flow (1)2 Material of helmet and explanationTough (1)e.g deforms plastically before breaking (1)2 Deformation(In crash energy, deform s/absorbed by helmet rather than causing injury (1)1[9]14.(a)Proportional / Hookes law limit (1)1(b)Stiffness of sample (1)1(c)Work done / strain energy (1)To stretch (OR strain) wire to fracture (1)2[4]15.(a)As skydiver speeds up, air resistance will increase (1)Net force on skydiver will decrease, reducing acceleration (1)2(b)Parachute greatly increases the size of the air resistance (1)When air resistance = weight of skydiver, skydiver is in equilibrium (1)2(c)Use of as v2 = u2 + 2as or mv2 = mgh (1)Correct answer [7.7 m s1] (1)Example of calculation:v = = 7.7 m s12[6]16.Spelling of technical terms must be correct and the answer must beorganised in a logical sequence (QWC)Mixing of layers leading to eddies/whorls (1)Air circulates around at edge of platform (1)Passenger may be pushed over due to eddies/whorls (1)[3]17.(a)Use of (1)Correct answer [1.44 106 kg] (1)Example of calculation:2(b)Use of mg = 6rv (1)Correct answer [1.2 m s1] (1)Example of calculation: (2)2[4]