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MODIFICATIONS – FORM 5CHAPTER 1

1. Design a good beach

Suggestion Explanationnear the bay divergence of the waves energy /calmerHigh retaining walls Over flow

To reflect the waves from the shoreReduce direct impact of the waves on the shore

Wall from concrete reduce erosion are builtConcrete barrier structure with a gap Waves passing through the gap will be diffracted in the

children’s area.-reduce amplitude

Tambak laut supaya lebih cetek Reduce speedMore number of tree Diffraction occur will reduce tha amplitudeUneven surface of retaining wall Reduce energy

2. Suggest and explain how ordinary fishing boat can be upgrade to the new boat which complete equipment to detect the crowd of fish.

Suggestion ExplanationAttach radar system to the ship

a) Ultrasonic transmitter

This equipment needs to detect crowd of fish and for measurement the depth of the crowd of fish-Use to produce ultrasonic pulses

a) Microfone reciever To detect ultrasonic pulsesb) CRO -To measure the depth of fish by calculating d=vt/2;

d=depth, v=velocity, t=timeUse ultrasonic wave -Ultrasound not produce sound

-Ultrasonic wave has higher frequency, more energy, so it can move further

Use high energy wave The penetrating power is higher

3. Explain the suitable design or method to build quality concert hall.

Suggestion ExplanationCover the hard wall with soft board or thick curtain

Soft surface can absorb sound and reduce reflection of sound

Place the wall with hole or egg carton design Can reduce reflection of sound so sound will be clearer/reduce echo

Fixed 2 loud speaker in concert hall Loud speaker can act as coherent sources for constructive inteference

Arranged the sit at antinodal place Strong sound can be heardUse glass or mirror hall which is the type which are not easily broken

Sound with high frequency might break the glass

Use special computer to generate sound wave which produce destructive inteference

Audience can enjoy better presentation without disturbance

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4. Explain the suitable design of retaining wall to protect the ship at the harbor

Suggestion ExplainationBuild concrete retaining wall Can withstand impact of the wave, difficult to crackRetaining wall should be curved and uneven surface

Prevent reflection of wave back to the ship

Build retaining wall in front of the bay The wave are calmer at thr regionRetaining wall has gap Diffraction will occurThe gap at retaining wall is narrow( smaller than wave length)

The greater the curvature of wavefront will occur. Amplitude after passing gap is smaller

There are slope at the bottom of retaining wall At shallow region, the wavelength of wave is smaller, so the velocity of the wave smaller

Retaining wall should be build higher To ensure no spill over of waveBuild the jetty at bay The wave at bay is calmer

5. Explain the characteristics of parabolic radar system to detect signal from satellite communication.

Suggestion ExplanationLarge diameter size of parabolic disc Able to receives more electric signalType of wave transmited is Microwave Has high frequency, high energy, short wavelength so it is

easy to be reflectedThe distance of the signal receiver from the centre of parabolic disc is the same as the focal length

The signal can be focus to the centre of the parabolic disc

Place parabolic disc higher from the ground The signal with not be block by trees or anything and the signal easy to be detected

Place parabolic disc at clearplace No signal disturbance

CHAPTER 2

6. Suggest the suitable lamp that can be use in the library, cheaper yet become the room brighter

Suggestion ExplanationLamp with parallel circuit If any lamp were burn out, others can still be usedAttach shiny reflector Can reflect light more, no need to install more lamp, the

room will become brighter.Low power lamp Safe costHigh efficiency lamp // fluorescent The room looks brighterLong life span lamp No need to replace oftenLow price lamp Save money

7. Explain the modification of menthol bulb lamp to efficient lamp to be use in study room.

Suggestion ExplanationUse the fluorescent lamp not a filament bulb Fluorescent lamp use less power and economic (consume

less power) compare to filament bulb.Bigger cover with white colour Less reflection on eyes and absorb less heat energy and good

heat reflectorUse the adjustable stand or portable The height of the lamp can be adjusted can be used

anywhereConnect with the earth wire Avoid short circuit and damage on the bulbUse an energy saver lamp Produce same brightness with less power consumption

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8. Suggest the suitable design of fuse to protect an electrical equipment which is label 240V,2400W

Suggestion ExplanationThin fuse wire Less space/to carry a limited electrical current/less mass

hence low heat capacity/shorter time to heat up to melting point and blow

Ceramic cartridge Can withstand higher temperature because spark created by high voltage.240V can be huge

Fuse rating is 13A Maximum rating must be sligthly higher than normal currentLow melting point For fast blow/melting faster when excessive current

flow/easy to cut the current flowLow specific heat capacity The fuse wire easily heated,melt and break the circuitMetal is used Good electric conductorResistance to oxidation Does not interface with other function

9. You have to choose one of the cables to be used in the National Grid Network. Explain the suitability of each of the characteristics of the cables.

Suggestion ExplanationDiameter should be large To reduce the resistance of the cabledensity should be low The cables will be lighter and can be supportedsecurelyThe rate of expansion should be low So thre is less expansion and less sagging in the cables during

hot daysThe melting point should be high So the cables does not melt in high temperature

10. Explain the characteristic of electric pylon and the cable taht been use for electric transmission

Suggestion ExplanationMaterial: steel alloy Strong,will not break easilyV shape steel alloy Not too heavyTrust and supprt join Can support bigger weightMade from small diameter and laminated wire Reduce addy current Cable made from low density material Cable is not heavy/ light weight

11. Investigate the characteristic of electric oven that can toast more cupcakes at less time

Suggestion ExplanationThe space inside oven is build bigger It can fil up 180 slices of breadIncrease the number of resistance heater at the top and bottom

So it can supply enough heat

The wall is made of good insulator Tyhe heat will not lost to surroundingFix a fan inside the oven Heat energy releaswed can spread uniformly in ovenInternal space of oven is painted silver So the heat will radiated at wall and reflected back

completelyFix the step up transformer Oven can receive higher voltage and can function with higher

power

12. Explain the designof electric kettle

Suggestion ExplanationMaterial of heating is made from nichrome To produces high heat energyHigh number of loop To increase surface area so that more heat is releasedUse high power To produce more heat energy in the coilHigh melting point coil Nit easy melt under high temperatureLow rate of rusting Does not get rust easilyUse thermostat When temperatures reach 100oC3 plug in If short circuit the overload current flows to earth(for safety

reason)

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13. Design incubator used to hatch eggs

Suggestion ExplanationParallel circuit When one bulb damage the another bulb still function/heat can

distributed uniformlyMulti storey rack More eggs can be arrangedUsing fan heat can distributed uniformlyBulb with same brigthness and power heat can distributed uniformlyUsing alarm To ensure that correct timing is employed in the hatching of eggs

14. Design circuit for cabin or house

Suggestion ExplanationCircuit connected in parallel Allow each electric appliances to be switched on and off

independentlyFit fuse at the live wire in the fuse box To stop the flow of current by melting when a high voltage of

electric current flows through the circuit // switches itself off very quickly if the current exceeds e.g. 15A (for 15A mcb)

Earth connection to the metal case of electrical appliances

Earth wire connected to earth, so that when a fault occurs and a current flows through the live wire and the earth wire, the fuse in the live wire will blow and cut off the supply. It will protect a person who may touch a faulty or live appliance

Use low power lamps / install fluorescent lamp To save the energyRegularly cleaning and removing dust from the air filters of air conditioners// Do not put more water in a kettle than needed for hot drinks

To save the energy

CHAPTER 3

15. Suggest modification that need to be done on dc motor to increase efficiency of the motor.

Suggestion ExplanationLow density material Coil hass smaller mass/ lighterIncrease the number of turns in the coil

Can increase magnitude of force/ higher electromagnetic field strength

Use high strength of magnets/ Add more magnets

Increase the strength of magnetic field

More segments Coil rotates smoothlyIncrease the magnitude of current

Can increase the magnitude of force/ can increase the strength of magnetic field

16. Investigate the design and the characteristic to improve the efficiency of transformer.

Suggestion ExplanationUse soft iron core Easy to magnetized and demagnetizedLaminated core Less eddy current or reduce energy lostUse thick wire Reduce the resistance or more current flowUse copper wire to make coil Low resistance or reduce the lost of heatWind the secondary coil on top of the primary coil

Reduce leakage of field lines

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17. How to design a moving coil ammeter that can function better and able to detect small change of current?

Suggestion ExplanationUse stronger magnet Strong magnetic field or larger rotationUse curve magnet or concave Produce radial magnetic field/to get linear scaleUse cylindrical core To supply uniform magnetic fieldUse soft iron core To concentrate the magnetic fieldUse linear scale The angle of rotation is linearThe sensitivity of moving coil galvanometer can be increased by increasing the strength of the radial magnetic field

Increase the force between the current carrying coil and magnetic field

Using hairspring of lower stiffness Smaller opposing force to stop turning of coilUse lighter pointer Smaller inertia easier to moveUse a coil of a lighter mass Smaller inertia able to move easilyIncrease the area of coil More changes of magnetic flux,a bigger force are produce

18. Suggest and explain the build of adaptor to charge the 8V handphone from 240V power supply.

Suggestion ExplanationUse step down transformer Able to reduce voltageRatio of turns 30 : 1 // 240V:8V Can reduce voltage from 240V to 8VUse four diodes Full wave rectificationFull wave rectifier To convert au current to dc currentUsing a capacitor To smooth output current (steady direct current

CHAPTER 4

19. Suggest and explain the build of adaptor to charge the 8V handphone from 240V power supply

Suggestion ExplanationUse step down transformer Able to reduce voltageRatio of turns 30 : 1 // 240V:8V Can reduce voltage from 240V to 8VUse four diodes Full wave rectificationFull wave rectifier To convert au current to dc currentUsing a capacitor To smooth output current (steady direct current

20. Consult and modified the automatic switch light (diagram A) above which can switch on at night and switch off during morning to be automatic switch on fire alarm when there are fire , explain using diagram and the function of component.

Suggestion ExplanationChange R1 to termistor Thermistor can be detect heat from fireChange LED with alarm// siren Able to produce sound of alarm if fire is detectedChange LDR with R1 During fire, R1 has greater resistance compare to LDR so, no

current flowWhen the temperature is high, the resistance of thermistor is low. This will increase the voltage acroos R1. So, current will flow to the base of transistor , than the transistor is switch on followed by greater increase in collecter current. The alarm will switch on.

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21. Suggest the modification need to be done to the circuit in Diagram C so that it can function as automatically fire alarm switch that need high voltage.

Suggestion ExplanationReplace LDR with thermistor To detect heat when temperature is highReplace bulb with siren/bell To produce soundConnect relay switch to output transistor To switch on the sirenInterchange the position of resistor R and thermistor To increase base voltage//voltage across R//base currentUse 240 V power supply Siren is function as high voltage

22. Modified the circuit 240V and Np = 4000 turns circuit to switch on 12V d.c radio.

Suggestion ExplanationStep-down transformer Capable of reducing potential difference / voltageRatio of turns 20 :1 // 240:12 Np = 4000 turns and Ns = 200 turns

Reduce potential difference 240V to 12V

Using four diodes Full wave retificationUsing a capacitor To smooth out output current // produce output to steady

direct current.

23. Moving coil microphone

Suggestion Explanationuse thin diaphragm Easy to vibrateUse strong material Not easy to breakMore number of turns of coil Increase the rate of change of magnetic flux linkage // The

magnitude of the induced current or is also increasedThicker diameter of wire of coil reduce the resistance of the coilUsing more powerful magnet to increase the strength of the magnetic field.//Increase the rate

of change of magnetic flux linkage//The magnitude of the induced current or induced electromotive force is also increased

CHAPTER 5

24. Explain the suitability of characteristic of radioisotopes to be used as treatment in brain tumor radiotherapy?

Suggestion Explanation Short half life Radioactive is dangerous substance, short half lfe can decay fasterGamma ray radiation Gamma can kill cancerous cell and can penetrate skin of patientLow ionozing power Minimum damage to tissue organLiquid state of matter Easy to dissolveHigh penetrating power Can penetrate easily

12V,24W

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25. Suggest and explain the safety ways, which are required when handling radioactive substance.

Suggestion ExplanationUse thick lead box Radioactive rays evem gamma cannot pass throughUse forceps / robotic hand Avoid direct touchWear photographic film Able to detect exposure radiationsWear plumbum safety suit To protect the body from expose to radiationUse siren Faster warning when leakagePacked into concrete drum and buried underground

Prevent the radioactive waste discharge to environment

Always place GM detector nearby To detect the amount of radioactive nearby, for safetyLabel the radioactive container with symbol Easy to detect radioactive substance

26. Explain the suitability of characteristic odf radioisotope to be use in controliing the population of pest

Suggestion ExplanationUse gamma ray Able to mutate the insectSolid state of matter Easy to handleLong half life Last longerHigh penetrating power Able to penetrate thick object/materialHigh ionizing power Able to change// mutate the biology of insect

27. . Explain the suitability of characterisitc of radioisotopes to be used in th trace of water pipeline.

Suggestion ExplanationShort lhalf life Radioactive is dangerous substance, short half life can decay

fasterFew hour half life - Enough time for worker to detect the pipe leakage

- Radioactive uis dangerousBeta particle or Gamma ray radiation Can penetrate pipe and soil, can be detectedLiquid state Can be inject and dissolve into water

28. Suggest the design of nuclear reactor.

Suggestion ExplanationUse uranium-235 Use as nucler fuelNuclear fission A lot of heat will produceBoron or Cadmium rad use as control rods To control the rate of nuvlear fission and to stop the radiationUse moderator (graphitr) To slow the motion of neutron to the best reaction rate. So the

rate of nuclear fission can be controlledBulid thick concrete wall Lead or thick concrete wall can prevent the escape of radioactive

rays, keep the radiation inside the reactorCoarbon dioxide or water is use as coolong agent

To remove heat of reaction for turbine generator. This produce steam as heat carrier

Use steam To turn the turbine and able to generate current

29. Explain the suitability of charactersitic of radioisotopes to be used in sanitiza medical equip,ent

Suggestion ExplanationGamma ray Able to kill ant virus/ bacteriaLonger half life No need to change radioactive frequentlySilid state of matter Easy to handleHigh penetrating power Able to penetrate any equipment to sanitize

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30. Explain the suitability of characteristics of radioisotope to be used in detecting the position of blood clot in veins (Deep vein thrombosis)

31. Explain the suitability of characteristics of radioisotope to be use in the trace of blockage in the kidney patient.

Suggestion ExplanationUse Iodine-123 Used as nuclear imaging tracers to evaluate the anatomic and

physiology functionGamma ray Able to penetrate trough body, bones and be detectedLow energy Do not cause serious damage in cellsLiquid state of matter Easy to inject to patient bodyShort half life Active in body in short time

32. Explain the suitability of characteristics of radioisotope to be use in control the thickness of paper in factory

33. Explain the suitability of characteristics of radioisotope to be use in control the thickness of aluminium sheet in factory.

Suggestion ExplanationLong half life Can be used for long time, no need to replace frequently7 so, it save

costGamma ray Can be penetrate aluminium sheet and be detectedSolid state of matter Easy to handle, does not spill

Suggestion ExplanationUse liquid state of matter Able to inject into patient body, dissolve easilyShort half life Active in body in short timeUse beta ray Able to penetrate skinLow ionizing power Minimum damage to tissue organ

Suggestion ExplanationLong half life Can be used for long time, no need to replace frequently so, it save

costBeta ray Can penetrate paper and be detectedSolid state of matter Easy to handle

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MAKING DECISION-SECTION CSoalan ini berada di dalam Section C. Cadangan dan alasan dalam soalan ini juga boleh menggunakan contoh jawapan dalam soalan Modification.

34. The transmission of electricity over the National Grid Network uses high voltage cables. You are assigned to study the characteristics of cables which could be used as transmission cable. Table 12 shows the characteristics of four transmission cables. Determine the most suitable transmission cable to be used and give reasons for your choice.

Cable Resistivity /Ωm-1 Density / kg m-3

Cost Rate of thermal expansion

P 3.0 x l0-7 5 x l05 Low HighQ 1.8 x l0-8 2 x l03 Medium LowR 7.5 x l0-7 8 x l02 High MediumS 7.0 x l0-8 4 x l03 Medium High

AnswerCharacteristic Explanation

Low resistivity To reduce heat loss in the cables Low density The cables will be lighter Low cost Cost of project will be lower Low rate of thermal expansion The cables will not expand under hot weather

Cable Q is the most suitable transmission cable because of its low resistivity, low density, medium cost, low rate of thermal expansion.

35. You are required to build a hydrometer that can be used to measure densities of concentrated acids.Table 11.1 shows the characteristics of 4 types of hydrometers L, M, N and O. Decide which hydrometer is most suitable and give reasons.

Hydrometer Type of material of hydrometer

Diameter of capillary tube/ cm

Density of shots/ kgm-3

Diameter of bottom bulb/ cm

L Plastic/Plastik 0.5 1000 1.0M Plastic/Plastik 2.0 1300 3.0N Glass / kaca 0.5 9800 3.0O Glass/ kaca 2.0 8000 1.0

AnswerCharacteristic Explanation

Material made from glass Glass does not corrode with acidSmall diameter of capillary tube To increase the sensitivity of the hydrometerHigh density of shots Makes the hydrometer stays uprightBig diameter of bottom bulb To obtain a bigger upthrust.Choose N N is made from glass, has small diameter of capillary tube, high

density of shots and a big diameter of bottom bulb

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36. As a researcher , your duty is to study the characteristics of a material to make a water heater. You are given four choices of metal type T, U,V and W. The table below shows the characteristics of the four metals.Determine the most suitable metal to be used as the material to make the heater and give your reasons.

AnswerCharacteristic Explanation

Smaller surface area the resistance is higherHigh melting point not easy to meltLow specific heat capacity the temperature arises shortlyLong (coiled) metal to increase the resistanceChoose V because it has,smaller surface area, high melting point, low

specific heat capacity and long metal

37. You are given four choices of metals P, Q, R and S. The table below shows the characteristics for the four metals. Determine the most suitable metal to be used as the material to make the boat and give your reasons.

Metal Shape DensitySpecific Heat

CapacityStrength

P Streamlined 900 Low HighQ Oval 452 High HighR Circle 387 Low HighS Streamlined 500 High High

AnswerCharacteristic Reason

Streamline reduce the resistance of waterDensity higher buoyant forceSpecific heat capacity high absorbs heat slowlyHigh strength Difficult to damage

The most suitable metal to be used as material to make the boat is metal S because of its streamline, low density, high specific heat capacity and high strength.

38. A student plans to fix a lamp in his room. Table 12.1 shows the features of 4 different types of lamps. Explain the suitability of each feature in Table 12.1 and then determine the most suitable lamp to be used. Give a reason for your choice

Type of lamp Power Efficiency Life Span PriceCompact fluorescent lamp 18 W 50 % 7000 hours HighFilament lamp 75 W 12 % 1000 hours LowLong fluorescent lamp 20 W 45 % 14000 hours MediumRound fluorescent lamp 24 W 40 % 10000 hours High

AnswerCharacteristic Explanation

Low power lamp Safe cost//electric billHigh efficiency The room looks brighter//high output power//less power wastageLong life span No need to replace oftenLow price Save money/costLong fluorescent Low power with highest efficiency, long hours of life span and low

price

Metal The cross sectional area Melting Point Specific Heat Capacity LengthT Smaller Low High LongU Larger High Low ShortV Smaller High Low LongW Larger High Low Short

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39. Table 11.1 shows 5 materials which can be used to make an optical fibre. You are asked to investigate the characteristics of the materials in Table 11.1 which could be used to make the optical fibre.Explain the suitability of each characteristic and hence, determine the most suitable material to be used to make the optical fibre. Give a reason for your choice.

Material Refractive index % of light energy absorbed Rigidity Strength

P 1.75 2 % Strong WeakQ 1.80 10 % Weak StrongR 1.70 2 % Weak StrongS 1.52 3 % Strong StrongT 1.48 10 % Weak Weak

AnswerCharacteristic Explanation

High refractive index Total internal reflection can occur easilySmall amount of light energy being absorbed by the material

The object under observation can be seen clearly // more light can be transmitted

Material with weak rigidity The optical fibre can be bent easilyMaterial with great strength The optical fibre can last longer/not easily spoilMaterial R High refractive index, low % of light energy absorbed, weak

rigidity and great strength

40. You are asked to investigate the characteristics of hot air balloon as below. Explain the suitability for each characteristic for the hot air balloons and then determine which hot balloon will move up the fastest into the air. Give a reason for your choice

AnswerCharacteristic Explaination

Volume of the balloon is high Displace a larger amount of air/Produce a higher buoyant force.

Density of the balloon material is low Lower mass/LightGas temperature is high Produce a maximum expansion of balloon.Total of mass is low Upwards resultant force is higher/ Balloon move upwards faster.

Choose Q Because it has a high volume,the density of the balloon material is low,the gas temperature is high and the total mass is low.

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41. Table 11.1 shows the characteristics of five types of materials that can be used for making the soles of the trekking shoes. You are asked to study the characteristics of the materials shown in Table 11.1. Explain the suitability of each characteristics in Table 11.1 and then determine the most suitable material to be used. Give a reason for your choice.

Type ofmaterial

Density(Kg/m -3)

Number of studs x Area of 1 stud

Expansion effect

Ability to stretch

P 820 6 x 30 cm2 Low GoodQ 700 8 x 30 cm2 Low GoodR 720 5 x 30 cm2 Medium AverageS 750 4 x 30 cm2 High PoorT 880 3 x 30 cm2 High Poor

Answer

Characteristic ReasonsLow density Small mass/lightMany/fewer/very few studs Gives extra/higher gripExpansion effect is low Always fits/Does not loosen when hot.Ability to stretch is good Less stress on the feet/Can be pushed in all directions/

Can walk on uneven surface.The most suitable material is Q Because it has a low density,many studs,low expansion effect and

good ability to stretch.

42. Table 12.2 shows the characteristics of five radioisotopes P, Q, R, S and T. As a factory engineer, you are required to determine the most suitable radioisotope that can be used by the system to ensure the volume of guava juice is uniform.Study the characteristics of all 5 radioisotopes and explain the suitability of the aspects.Determine the most suitable radioisotope and give the reason for your choice.

RadioisotopeRadioisotop

Half lifeSeparuh hayat

Types of rayJenis sinar

State of matterKeadaan jirim

Ionising powerKuasa pengionan

P 7 hours alfa solid highQ 10 days beta liquid moderateR 100 days gamma solid lowS 10 years gamma liquid highT 30 years beta solid low

Answer

Characteristics ExplanationHas a long half-life Can be used for a long time hence save cost Emits beta Can penetrate box and liquid and is less

dangerous than gammaSolid form Easy to handle and contain.Low ionising power Does not change the state and taste of juice.Radioisotope T It has long half life, emits beta, in solid form and has low ionising power.

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43. You are assigned to investigate the design for the location to keep the boats andthe characteristics of the retaining wall as shown in Diagram 12.2 based on the following aspects:- the location to keep the boat- material used for the retaining wall- the height of retaining wall- size of slitExplain the suitability of the location and the characteristics of the retaining wall and determine the most suitable design to keep the boat safely.

AnswerCharacteristic Reasons

Bay Wave is calmerConcrete retaining wall Stronger/ / lastingHigh wall Prevent high waveSmaller opening/aperture / slit ofretaining wall

Diffraction obvious //low wave energy

Choose P At bay, concrete retaining wall , high wall and smaller slit

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44. Diagram 11.4 shows five designs of ‘Newton’s Cradle’, P, Q, R, S and T, with different specifications. You are required to determine the most suitable design to make the ball at the end swings up to higher level and at bigger speed. Study all the five designs from the following aspects:− The arrangement of the balls − The type of material used to make the balls− the number of string used to hang the balls − the position of the ball to start the oscillation

AnswerCharacteristic Reasons

The balls touch each other This will reduce losses of energy which will reduce the speed of theballs

The type of material used to make theballs is steel

Steel balls are hard and produce highly elastic collision. Energy caneasily propagates through the intermediate balls.

Two strings used to hang each ball This string arrangement restricts the balls’ movements to the same plane. the position of the ball to start the oscillation

High position of the ball High potential energy and will change to high kinetic energy. The last end ball will swing at bigger speed.

The most suitable design is Q because the ball s touch each other, made from steel, use two strings attached to each ball and the initial position of the ball is high