modification 2022

Modification/ Decision Making pg - 1

1. Explain the suitability feature of arm exercise equipment.

Suggestion Explanation

Steel spring Can withstand higher force

Two// more spring Stiffer, share the load equally

arrange in parallel

Spring with ticker wire Will not easily break

Smaller diameter coil Less elastic

of spring

Larger force constant Stronger spring, stiffer

2. Suggest the suitable cloth, equipment and techniques to
improve high jumper athlete’s performance and their

safety.

Suggestion Explanation

Tight and light suit Less air fraction

Spikes shoes Better grip support while running,

prevent slippery

Thicker mattress Increase time impact, reduce

impulsive force

sprint before jump Can increase kinetic energy//

increase momentum

bend the body during Increase the time of impact, reduce

fall impulsive force

Landed flat on the Increase surface area of contact//

mattress reduce pressure

Modification/ Decision Making pg - 2

3. Suggest and explain the build of water bottle rocket in

school competition to move higher altitude and has longer

time on the air.

Suggestion Explanation

The body of rocket Do not break easily under high

must be strong pressure

Smaller mass accelerate faster

streamline/aerodynamic Reduce air resistance

shape

Nose cone or bullet To improve the aerodynamic of

shape on top of body rocket

angle of launching 45º The rocket can travel maximum

distance

The volume of water is To increase momentum and

half or 1/3 from the impulsive force

whole volume

Attach 3 or 4 fins at the Rocket will move smooth and

tail of rocket equally stable

Attach parachute longer floating time on the air

before landing

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4. An earth-monitoring satellite falls into the earth’s

atmosphere at a high velocity and reaches a high
temperature. This is caused by the earth’s gravitational force

and air resistance. Using the appropriate physics concepts,

suggest and explain suitable designs or ways to protect the

satellite and its equipment.

Suggestion Explanation

Aerodynamic shape To reduce air resistance

Heat shield To protect the capsule

High melting point Do not melt

Landing in water // Increase time of impact// Reduce

soft ground impulsive force

Light material // small Reduce the inertia // reduce the

mass //low density momentum

Parachute / Retro To reduce speed

rocket

strong material//stiff Withstand larger force while

composite landing

Modification/ Decision Making pg - 4

5. Give suggestion to improve the design of jet engine so that it

can be use for larger airplane at the higher speed.

Suggestion Explanation

Increase more fuel More fuel to be burnt to produce

injectors greater force

Increase the size of the More space for fuel to burnt

combustion chamber

Decrease the diameter Exhaust gas ejected at higher

of the nozzle velocity

Increase the speed of Increase the air intake

blade/use bigger blade

Blade and engine made Can withstand strong pressure,
of strong materials won’t break easily

6. Explain the most suitable design of motorcycle that can

move fast, safe and save time in racing.

Suggestion Explanation

Lower seat height Lower center of gravity

Bigger width of tyres Bigger surface area, reduce

pressure

Less thread pattern reduce friction of tires on road

Smaller mass Lighter

With ABS does not stop immediately

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7. Suggest the design of roller skate track so it can be used to

oscillate skate continuously.

Suggestion Explanation

Semicircular curve Exchange between kinetic energy

shape and gravitational potential energy

easily

Smooth surface Reduce frictional force

The slope slightly Easy to oscillates cause by

increase and decrease changing of energy

Use strong material Withstand high impact such as

such as concrete of high force of jumping and landing

foundation of the track

Soft layer at the Reduce impulsive force

surface

8. Explain the characteristic of spring to make baby’s cradle.

Suggestion Explanation

Large force constant Stronger, stiffer and not broken

spring easily

Large diameter of wire Stiffer

Large diameter coil of More elastic

spring

made of steel or alloy Stiffer

The arrangement of The spring is stiffer, load is share

spring is two or more equally

line in parallel

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9. Suggest the suitable cloth and the best techniques to catch

ball to prevent injury for goalkeeper.

Suggestion Explanation

Wear glove Lengthen the time of impact,

reduce the impulsive force acting
on the player’s hands

Use soft material for Lengthen the time impact, reduce

glove impulsive force.

Wear cloth which is absorb more heat to maintain the

made from high temperature of player.

specific heat capacity

material

Base of shoes has stud Greater pressure, avoid slipping.

When catching the Lengthen the time impact between

ball, the goal keeper ball and hand, reduce the impulsive

should move his hand force.

backwards

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10. Explain the most suitable design of spring for shock

absorber for motorcycles.

Suggestion Explanation

Small diameter of Larger space for the spring

spring coil

Large diameter of Stiffer

wire(thicker)

Larger force constant Smaller compression of the spring,

able to support larger weight

Small natural To reduce bumping

frequency

11. Modified the ship that can carry more and heavier load,

move faster and safe while travelling.

Suggestion Explanation

Strong material Can withstand great force

Low density material Light weight

Has more than two Safe to travel on the fresh and salt

stage, plimsoll line water

Big size Can place more goods

Aerodynamic/ Reduce water friction.

streamline shape

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12. Suggest how to increase the safety for motorbike racer

to reduce injuries/ accident

Suggestion Explanation

Use helmet To protect the head

Use helmet with hard spreading the impact with hard

outer casing and soft outer casing and absorb energy

inner liner with soft inner linear of Styrofoam

Use safety jacket To protect from injuries

Use gloves To protect the hand

Use padded leathers Will soften any impact and protect

suit the skin from abrasion

13. Explain the design of kayak which can travel faster and

safer.

Suggestion Explanation

Streamline Reduce water resistance

/aerodynamic shape

Smooth surface body Reduce friction of body towards

/coated with wax water

Low density material Lighter, easier to float, easy to

carry

Strong material body Last longer, not easily broken

and peddle

Wider peddle surface Greater force because more water

are peddled up

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Wear safety jacket Passenger can float and safe if they
fall into water.

14. Explain the suitable loaded lorry which can carry liquid,

such as petrol.

Suggestion Explanation

The load of lorry To reduce effect of inertia

should be divided into

many smaller tank

The load must be tied So it will not fall of from the lorry

Far gap distances Prevent collision between tractor

between tractor and and trailer, easier when turning

trailer

Use more tyres for Pressure will be separate to all

lorry tyres, more stable.

Small belt behind lorry To discharge spark, prevent from

burning the petrol

Use Antilock Brake The lorry can stop easily without

System (ABS) skidding

Modification/ Decision Making pg - 10

15. Using physics concept, suggest and explain suitable

athletes attires, running, jumping, landing techniques and

other aspects to help the long jumper can jump further.

Suggestion Explanation

Use tight and light suit Less air friction

Use spike shoes Better grip support while running,

prevent slippery

The athlete have to Can increase the kinetic

sprint before jump energy//momentum

The athlete have to Increase the elastic potential

push the body in front energy//able to increase longer

while jumping distance of jumping

Athlete have to bent Increase the time impact, reduce

the body during fall impulsive force, less injured

16. Give suggestion to design a sail boat which can travel

faster and smooth.

Suggestion Explanation

Streamline Reduce water and air resistance

/aerodynamic

Smooth surface Reduce friction toward water

board/coated with wax

Low density material Lighter, easier to float

Strong material Withstand strong wind, not easily

damage

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Wider sail Greater lifting force because more
wind are captured

17. Explain how you would design the pile driving

system[the ram hammer is lifted to a height by the crane and

allowed to fall on the pile]

Suggestion Explanation

Large hammer weight Large momentum when it hit the

pile

Ram hammer made Not break easily/last longer

from hard material

such as alloys

Hammer raised at Increase the gravitational potential

higher position energy

Stronger end of the top Will not break easily

of the concrete pile

Sharp end of the To increase the pressure

bottom of the concrete

pile

Modification/ Decision Making pg - 12

18. Explain the characteristic of material to be use for making

the sole of jungle trekking shoes.

Suggestion Explanation

Rubber sole Good impact absorber

Low density Light weight

Many stud Give extra grip

Low expansion effect Not loose easily

Good ability of stretch Comfortable to feet, foot can move

unstressed

19. Explain the design of hydrometer which can be use to

determine a wide range of densities of liquid.

Suggestion Explanation

Small stem and long Able to detect smaller change,

increase sensitivity

Glass wall Do not erode and small adhesive

force

Large diameter of bulb Higher upthrust / displaces more

liquid / able to float easily

Scale can be made Ability to measure a wide range of

bigger or smaller than densities of liquids.

the density of water.

-The hydrometer is

floated in alcohol.

The liquid level at the

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stem is marked (upper

level)

-Then, the hydrometer

is floated in higher

density liquid like

mercury and marked

(lower level)

Lead shots can float upright, more stable

20. Efficient brake system.

Suggestion Explanation

Type of liquid: oil Uncompressible

Thickness of brake To withstand the high pressure

line: high from the liquid

The ratio of cross To produce larger force on wheel

sectional area for piston

wheel piston and

master piston : high

The chosen of type of Disc brake is more efficient than

brake for front & rear drum brake

wheel:

Front wheel - disc

Rear wheel - drum

Modification/ Decision Making pg - 14

21. Describe the suitable design to build a tent which will be

construct at open space for a week.

Suggestion Explanation

Choose low density Light weight and strong

metal for frame

Use hollow rod which Hollow rod is not heavy, easy to

can assemble easily carry, faster to build, can reduce

the cost of construction and

transport

Water proof canvas If raining, would not getting wet

Anti rust rod Can withstand rain and long lasting

Sharp end rod Small surface area, exert higher

pressure to ground, the tent can be

planted into ground firmly

22. Explain the necessary modification for the structure of

dentist chair for children that are suitable and safe.

Suggestion Explanation

the cross-sectional area to lift heavier load / to increase

of force multiplier of system

-big piston : bigger

-small piston : smaller

The wall of pipe is To withstand the high pressure

made up of strong

alloy

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The surface area of the To support the weight of people

seat enlarged

Use non-corrosive oil So that the wall of the pipe will not

in jack be corroded and cause leakage

Type of liquid: oil Uncompressible, more efficient

23. Explain the build and design of hot air balloon which can

fly higher altitude faster and suggest some safety aspect.

Suggestion Explanation

Large balloon Produce bigger buoyant / upthrust

force, increase the volume of air

displacement

Many hot air burner Heat up the gas inside faster

Synthetic nylon Air proof, light weight and strong

balloon material

Gas temperature is Reduce the density of air in balloon

high

Total of mass is low Balloon move upward faster

Rattan basket Longer the time impact, reduce the

impulsive force to passenger when

landing

Fly on early morning The temperature outside the

or late afternoon balloon is cooler compare to the

inside of balloon, so the balloon

will rise higher

Modification/ Decision Making pg - 16

24. Explain the basic structure of submarine that can be use

for underwater exploration.

Suggestion Explanation

Strong material Does not break easily

Aerodynamic shape Reduce water resistance

Thick wall Withstand high water pressure

High density materials Increase mass, can submerge easily

Ballast tank To increase or reduce weight

Sonar transmitter and To estimate and depth

receiver

Attach periscope To view surrounding area when

submarine float

Use nuclear power to Cheap and lasting power

generate power

25. Modified the passenger airplane to cargo airplane that

needs to carry more load, less use of fuel.

Suggestion Explanation

Larger size of the body To increase the space

Longer length of wing To increase the upthrust

Increase the thickness To stand higher pressure difference

of the body

Use a more powerful To overcome inertia and do more

engine work per unit time

Increase the number of To support higher mass or pressure

tyres while landing

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Pilot has ejected seat To save the pilot if plane crash

during emergency happened

26. Using physics concept, explain necessary deep sea diving

suit and other accessory to carry.

Suggestion Explanation

Choose strong helmet To withstand high pressure of

with thick metal and water, protect the head.

glass to cover head

Use thick glass in front Enable the diver to see surrounding

of diver face and at the same time able to

withstand the water pressure.

Bring along gas To provide oxygen to diver to

containing mixture of breath

oxygen

Use very heavy suit The diver enable to stand on the

floor of ocean against the

buoyancy of water

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27. Design Vacuum Cleaner.

Suggestion Explanation

Large fan driven Increase the speed and amount of

airflows

Powerful of electric Increase the speed and amount of

motor airflows

Narrower inlet Increase the velocity/decrease air

opening pressure

large filter to block To have many pores for air to flow

dust particles while through

allowing air

molecules to pass

through

Larger spaced for Ensure that the air flows through the

depositing and filter is not block by too many dust

collecting the dust particles

particles

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28. Design hydraulic jack.

Suggestion Explanation

Bigger cross sectional Produced higher force

area of slave piston

(big piston)

Small cross sectional Less forced is needed/produced

area of master piston bigger pressure

(small piston)

Longer handle Less forced is needed to press small

piston(master piston)

Low density of a body Lighter

Type of liquid : oil Non-compressible

Release valve Liquid can flows into small

between small and reservoir easily when push the reset

main reservoir (reset) button.

29. Design paint sprayer

Suggestion Explanation

Large size of air Compress more air/can exert large

vessel pressure

Rubber material for More elastic/easier to squeeze

the vessel

Narrow shape of the Air can move with high speed

tube

Fiber glass material Stronger and last longer

for the rod

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Size of nozzle is The paint can be sprayed evenly
narrow at the end

30. Suggest the characteristic of material to build food

container which can keep the food warm.

Suggestion Explanation

low density material Lighter

High melting point Avoid from melting

Specific heat capacity The container will not get hot easily.

should be high

Low thermal Safe to touch

conductivity

Double wall Good heat insulator. The heat will

not loss and the food remain hot.

31. Explain the design and the characteristics of the cooking

pan.

Suggestion Explanation

Base is made of a Copper has a lower heat capacity,

copper become hot quickly

High density of base Heavier base make the pot stable

Body is made of Low specific heat capacity,

aluminium becomes hot very quickly. Low

density.

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Handle is made of High specific heat capacity, the

wood or plastic handle do not become hot

Low density material Lighter, does not add much to the

for handle total weight of pot

Transparent pot cover Able to see the food clearly. Food

cover will trap the heat

32. Modified and explain the design of an efficient solar

water-heating system on the roof.

Suggestion Explanation

Pipe embedded in Greater surface area which can

plate must be long absorb heat faster

Use metal pipe as Good heat conductor, so heat will

pipe inside the plate easily transmit to water

Use insulator behind Insulator will prevent the heat loss

the absorber panel

Black absorber panel Black is good heat absorber

Cover the top of the Heat will trap inside due to green

panel with glass house effect

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33. Suggest and explain the design of water heater to boil a

large quantity of water faster, efficient and safely.

Suggestion Explanation

Use tungsten High melting point

Coiled Longer wire, increase the resistance

High melting point Not easy to melt

Lower rate of rusting Does not get rust easily

Use thermostat When temperatures reach 100 ºC,

the water heater will automatically

turn off

34. Investigate the most suitable liquid that can be use as

coolant for car engine using physics concept.

Suggestion Explanation

Low freezing point Will not freeze easily during winter

liquid weather

High boiling point Do not easily boil when absorbing

liquid heat from the engine

High specific heat Can transfer large contain of heat

capacity liquid with a small rise in temperature.

Low ability to react The metal part of the engine will not

with metal corrode easily

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35. Most suitable design of clinical thermometer.

Suggestion Explanation

Use mercury Colour and opaque, easy to read

The scale range from To measure human body heat

35°C to 42°C

Small diameter of Mercury can expand at high rate for

capillary tube// extra a small change in temperature//

fine bore tube more sensitive

Use thin glass wall of Alow heat transferred easily

bulb

Use round glass stem Act as magnifying glass. So,

and wall mercury can be seen clearly

36. Suggest the design of heating system in the house and

characteristics of heating agent.

Suggestion Explanation

Use strong material Not easily break

Use metal pipe with Increase the rate of heat transfer

good heat conductor

Increase length of Can transfer the heat faster to

cooling coil surrounding

greater boiling point Liquid not easily change into

liquid vapour

Low rate of rusting Long lasting, not easily rust

material

Modification/ Decision Making pg - 24

The bigger size of Can blow and cool down larger

radiator fan area

Pipe in coil structure is Increase the time of flow and

used increase the quantity of heat

transferred.

37. Explain the build of solar cooker oven to boil 500 ml

water in short time.

Suggestion Explanation

Build the solar cooker The light will reflect to the cooker

with shiny// silver and heat up the water

colour reflector inside

Use metal cooker Good conductor

Paint the outside part To absorb heat

of the solar cooker and

the cooker (contain

water) with black

colour

Wrap the cooker with Avoid heat from release to

plastic or glass surrounding

Modification/ Decision Making pg - 25

38. Determine the modification to be made for container, so

the cut fruit will keep cool; remain fresh and easily seen.

Suggestion Explanation

Use container with Reduce the loss of heat from the

high specific heat container

capacity

Place small ice packet Ice able to absorb a large amount

below the bottom the of latent heat when melting

cut fruits

Add salt to the packet To increase the freezing point of

of ice ice, reduce the rate of melting

White wall colour of Can avoid absorption of heat from

container the surrounding

The container has Avoid heat from surrounding

double wall transferred easily to container. The

inside container remains cool

Transparent wall of The customer can see and choose

container in front of the cut fruits easily

customer

Modification/ Decision Making pg - 26

39. Explain how the design of radiator of the car and

characteristic of cooling agent which can absorb heat at

short time

Suggestion Explanation

Increase the Can transfer the heat faster to the

length/area of cooling surrounding

coil

Increase the number of Can cool down faster

fin blades

Use larger fan Can cool down larger area
Use cooling agent It won’t boil easily in high

liquid with greater temperature

boiling point

Use cooling agent Able to absorb large amount of

liquid with higher heat

specific heat capacity

Modification/ Decision Making pg - 27

40. Explain the characteristic and design of thermos flasks to

maintain hot water.

Suggestion Explanation

Use hollow plastic Able to trap air as air is poor heat

stopper conductor. Less heat loss.

Vacuum space Prevent heat loss through

conduction or convection

double wall Has vacuum in between the wall.

Heat not easier pass through the

wall of thermos.

Double walled tube Shiny surface reflect heat from the

coated with shiny paint wall of thermos flasks back to

water. So the water remains hot.

Double walled made of Glass is bad conductor. It will

glass reduce heat loss.

41. Explain the suitable characteristic of the mirror to be use

as outdoor safety mirror at the corner of the road.

Suggestion Explanation

Use convex mirror Wider field of view

Excellent weather Able to withstand bad weather

resistance

Excellent impact Save cost, last longer

resistance of material

Bigger size mirror To enable a wider view and sharper

image

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Greater reflectivity of Clearer image even in bad weather
material
Place at the sharp road To minimize from accident occur,
corner to enable the motorist see the
oncoming traffic

42. Determine and explain in the build of magnifying glass to

be use for enlarging the image of stamp

Suggestion Explanation

Choose convex lens The image will magnify

Excellent clarity of The image is clearer

lens

Small focal length Able to focus nearer

Bigger diameter of Allow more lights passing through

lens the lens

The object is place less The image form is magnify, virtual

distance than focal and upright

length

Modification/ Decision Making pg - 29

43. Explain the suitability of the mirror that is use in shop to

watch over the customer.

Suggestion Explanation

Use convex mirror Wider field of view

Greater reflectivity of Clearer image

material

Choose a bigger size Enable wider view and sharper

of mirror image

Place the mirror at the Easier to look at and won’t disturb

corner of shop ceiling the customer pathway

Low density Lighter to hang up

44. Design fibre optic.

Suggestion Explanation

refractive index of So that total internal reflection can

outer layer < refractive happen in the fiber optic.

index of inner layer

Use high flexibility so that it can be bend easily

material

Use strong material do not break easily

Use thin material Lighter//can be use in small area

Low density material Lighter

Modification/ Decision Making pg - 30

45. Determine and explain the build of telescope using lens J

and K with lens K is thicker than lens J which produce

bigger and clearer image.

Suggestion Explanation

Choose lens K as Lens K is thicker than lens J.

eyepiece lens Focal length of lens K is shorter

than lens J.

Light ray is refracted more in lens

K than Lens J.

Choose lens J as Has larger surface area, allow more

objective lens// Use light enter.

bigger diameter lens as Has a longer focal length.

objective lens

Use low power convex Magnification of telescope = fo
fe
lens as the objective
lens Low power lens has a longer focal
length, fo higher, magnification

higher

Use high power High power lens has a shorter focal

convex lens as the eye length, fe higher, magnification

lens higher

Use bigger diameter of Allow more light enter the

objective lens telescope

Modification/ Decision Making pg - 31

46. Determine and explain the build of Astro disc using

appropriate physics concepts.

Suggestion Explanation

convex curve parabolic The signals focused at one point

All signals are focus Better reception

on focal point

Smooth surface of disc Better reflection

Clean surface of disc, Better reflection

no water drop or dirt

47. Determine and explain the build of microscope using lens

P and Q with focal length of 15 cm and 5 cm respectively.

Suggest modification that need to be done to get brighter and

bigger image.

Suggestion Explanation

P as eye piece and Q as Focal length of P is longer than Q

objective lens

fo < u < 2fo produce real, inverted and

magnified image

Adjusted so that u < fe produce virtual, inverted and

bigger image// acts as a magnifying

glass

Distance between To produce bigger image from the

lenses > fo + fe eyepiece // to increase the

magnification

Modification/ Decision Making pg - 32

Store in a cool and dry avoid formation fungus at the
place lenses
Use more powerful// To produce bigger image
shorter focal length
lenses To produce brighter image
use bigger diameter of
objective lens

48. Modified the slide projector that need to be place in

school hall and can be seen by many student with clearer

image.

Suggestion Explanation

Use higher power bulb Higher intensity of light or more

light produced

The filament of the The light focuses at one point//

bulb is at the focus parallel ray can be obtained after

point of the concave reflection by concave mirror

mirror

More curvature More light to be reflected

(upward)// less light toward other

direction other than upward

Lens between f and 2f To produce real and enlarge or

bigger images

Increase the distance Larger image produced

or further away the

screen

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Electric fan operates Cooling system to stabilized the

during and after the temperature (heat energy produced

lamp is switches on by filament bulb) to increase the

projector lifetime

Use condenser mirror To concentrate more light to the

slide

Use a concave mirror Focus the light directly to the

instead of plane mirror lens//increase the intensity of light

Place the filament at Light goes directly from the lamp

centre of curvature of and reflect back on the same path //

the converging mirror increase the intensity of light

// use high powered toward the transparency // to get

lens brighter image

Use heat filter To absorb excess heat to the

transparency

49. Design a good beach.

Suggestion Explanation

near the bay diverge the energy of waves// sea

calmer

High retaining walls Avoid flooding/over flow

Wall from concrete Stonger //reduce direct impact on

the shore//reduce erosion

Concrete barrier Waves passing through the gap will

structure with a gap be diffracted // reduce amplitude

(energy) of waves

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More number of tree Reduce erosion
Uneven surface of Reduce energy of waves
retaining wall

50. Suggest and explain how ordinary fishing boat can be

upgrade to the new boat which complete with equipment to

detect the crowd of fish.

Suggestion Explanation

Attach radar system to a) Use to produce high frequency

the ship with ultrasonic pulses

a) Ultrasonic b) To detect ultrasonic pulses

transmitter c) To measure the time taken of

a) Microfone reciever reflected sound

b) CRO

Use ultrasonic wave higher frequency, less diffraction,

able to travel in a straight line/

travel further

Use high energy wave High penetrating power

Modification/ Decision Making pg - 35

51. Explain the suitable design or method to build a quality

concert hall.

Suggestion Explanation

Cover the hard wall Soft surface can absorb energy of

with soft board or sound// reduce reflection

thick curtain

Place the wall with Can reduce reflection of sound

hole or egg carton //reduce echo

design

Fixed 2 loud speaker Loud speaker act as coherent

in concert hall sources for constructive

interference

Distance between loud The positions of constructive and

speaker is further destructive interference are closer

together until they are hardly

noticeable

Arranged the sit at Louder sound can be heard

antinodal place

Modification/ Decision Making pg - 36

52. Explain the suitable design of retaining wall to protect

the ship at the harbor.

Suggestion Explanation

Build concrete stronger, difficult to crack

retaining wall

Retaining wall should Prevent reflection of wave back to

be curved and uneven the ship

surface

Build retaining wall in The wave are calmer at the region

front of the bay

Retaining wall has gap Diffraction will occur

The gap at retaining The greater the curvature of

wall is narrow (smaller wavefront will occur. Amplitude

than wave length) after passing gap is smaller

There are slope at the At shallow region, the wavelength

bottom of retaining of wave is smaller, so the velocity

wall of the wave smaller

Higher retaining wall To ensure no spill over of wave

Build the jetty at bay The wave at bay is calmer

Modification/ Decision Making pg - 37

53. Explain the characteristics of parabolic radar system to

detect signal from satellite communication.

Suggestion Explanation

Large diameter of Able to receive more signal

parabolic disc

Type of wave high frequency, high energy, easy

transmitted is to be reflected

Microwave

The distance of the The signal can be focus to the

signal receiver from centre of the parabolic disc

the centre of parabolic

disc is the same as the

focal length

Place parabolic disc The signal with not be block, easy

higher from the ground to be detected

Place parabolic disc at No signal disturbance

clear place

Modification/ Decision Making pg - 38

54. Suggest the suitable lamp that can be use in the library,

cheaper and the room become brighter

Suggestion Explanation

Lamp with parallel If any lamp were burn out, others

circuit can still be used

Attach shiny reflector Can reflect light more

Low power lamp Safe electrical energy

High efficiency lamp// Reduce the waste energy as heat
fluorescent

Long life span lamp No need to replace often

Low price lamp Save money

55. Explain the modification of menthol bulb lamp to efficient

lamp to be use in study room.

Suggestion Explanation

Use the fluorescent Fluorescent lamp use less power

lamp not a filament and economic (consume less

bulb power) compare to filament bulb.

Bigger cover with Less reflection on eyes// absorb
white colour less heat energy// good heat
reflector

Use the adjustable The height of the lamp can be

stand or portable adjusted can be used anywhere

Connect with the earth Avoid short circuit and damage on

wire the bulb

Modification/ Decision Making pg - 39

Use an energy saver Produce same brightness with less

lamp power consumption

56. Suggest the suitable design of fuse to protect an electrical

equipment which is label 240 V, 2400 W

Suggestion Explanation

Thin fuse wire Less space/ less mass /shorter time
to heat up to melting point

Ceramic cartridge Can withstand higher temperature

Fuse rating is 13A Maximum rating must be slightly
higher than normal current

Low melting point For fast blow/melting faster when
excessive current flow

Low specific heat The fuse wire easily heated, melt

capacity and break the circuit

Metal is used Good electric conductor

Resistance to oxidation Does not interface with other
function

Modification/ Decision Making pg - 40

57. Explain the characteristic of electric pylon and the cable

that been use for electric transmission.

Suggestion Explanation

Material; steel alloy Strong, will not break easily

V shape steel alloy Not too heavy

Trust and support join Can support bigger weight

Made from small

diameter and Reduce eddy current

laminated

Cable made from low Cable is not heavy/ light weight
density material

58. Investigate the characteristic of electric oven that can

toast more cupcakes at less time.

Suggestion Explanation

Bigger space inside It can fill up 180 slices of bread
oven

Increase the number of

resistance heater at the So it can supply enough heat

top and bottom

The wall is made of The heat will not lost to

good insulator surrounding

Fix a fan inside the Heat energy released can spread

oven uniformly in oven

Modification/ Decision Making pg - 41

Internal space of oven So the heat will radiated at wall
is painted silver and reflected back completely
Fix the step up Oven can receive higher voltage
transformer and can function with higher power

59. Explain the design of electric kettle

Suggestion Explanation

Material of heating is To produces high heat energy

made from nichrome

High number of loop To increase surface area so that

more heat is released

Use high power To produce more heat energy in the

coil

High melting point coil Not easy melt under high

temperature

Low rate of rusting Does not get rust easily

Use thermostat When temperatures reach 100°C

3 plug in If short circuit the overload current

flows

Modification/ Decision Making pg - 42

60. Design incubator used to hatch eggs.

Suggestion Explanation

Parallel circuit When one bulb damage the another

bulb still function/heat can

distributed uniformly

Multi storey rack More eggs can be arranged

Using fan heat can distributed uniformly

Bulb with same heat can distributed uniformly

brightness and power

Using alarm To ensure that correct timing is

employed in the hatching of eggs

61. Design circuit for cabin or house.

Suggestion Explanation

connected in parallel Allow electric appliances to be

switched on and off independently

Fit fuse at the live wire To stop the flow of current by

in the fuse box melting when a high voltage of

electric current flows

Earth connection to the when a fault occurs and a current

metal case of electrical flows through the live wire and the

appliances earth wire, the fuse in the live wire

will blow and cut off the supply. It

will protect a person blow and cut

off the supply.

Modification/ Decision Making pg - 43

Use low power lamps / To save the energy
install fluorescent
lamp
Regularly cleaning and Increase the efficiency of electrical
removing dust from appliances// To save the electrical
the air filters of air energy
conditioners

62. Suggest modification that needs to be done on dc motor to

increase efficiency of the motor.

Suggestion Explanation

Low density material smaller mass/lighter

Increase the number of Can increase magnitude of force/

turns in the coil higher electromagnetic field

strength

Use high strength of Increase the strength of magnetic

magnets/ Add more field

magnets

More segments Coil rotates smoothly

Increase the magnitude Can increase the magnitude of

of current force/ can increase the strength of

magnetic field

Modification/ Decision Making pg - 44

63. Investigate the design and the characteristic to improve the

efficiency of transformer.

Suggestion Explanation

Use soft iron core Easy to magnetized and

demagnetized

Laminated core Less eddy current or reduce energy

lost

Use thick wire Reduce the resistance or more

current flow

Use copper wire to Low resistance or reduce the lost of

make coil heat

Wind the secondary Reduce leakage of field lines

coil on top of the

primary coil

64. How to design a moving coil ammeter that can function

better and able to detect small change of current?

Suggestion Explanation

Use stronger magnet Strong magnetic field or larger

rotation

Use curve magnet or Produce radial magnetic field/to get

concave linear scale

Use cylindrical core To supply uniform magnetic field

Use soft iron core To concentrate the magnetic field

Use linear scale The angle of rotation is linear

Modification/ Decision Making pg - 45

increasing the strength Increase the force between the
of the radial magnetic current carrying coil and magnetic
field field
Using hairspring of Smaller opposing force to stop
lower stiffness turning of coil
Use lighter pointer Smaller inertia easier to move
Use a coil of a lighter Smaller inertia able to move easily
mass
Increase the area of More changes of magnetic flux, a
coil bigger force are produce

65. Suggest and explain the build of adaptor to charge the 8V

handphone from 240V power supply.

Suggestion Explanation

Use step down Able to reduce voltage

transformer

Ratio of turns 30: 1// Can reduce voltage from 240V to

240V:8V 8V

Use four diodes Full wave rectification

Full wave rectifier To convert au current to dc current

Using a capacitor To smooth output current (steady

direct current)

Modification/ Decision Making pg - 46

66. Moving coil microphone.

Suggestion Explanation

use thin diaphragm Easy to vibrate

Use strong material Not easy to break

More number of turns Increase the rate of change of

of coil magnetic flux linkage // The

magnitude of the induced current

or is also increased

Thicker diameter of reduce the resistance of the coil

wire of coil

Using more powerful to increase the strength of the

magnet magnetic field// Increase the rate of

change of magnetic flux //The

magnitude of the induced current is

increased

Modification/ Decision Making pg - 47

67. Consult and modified the automatic switch light (diagram
A) below 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 Explanation

Change R to termistor Thermistor can be detect heat from

fire

Change LED with Able to produce sound of alarm if

alarm//siren fire is detected

Change LDR with R During fire, R has greater

resistance compare to LDR so// no

current flow

When the temperature is high, the resistance of thermistor is

low. This will increase the voltage across R. So, current will

flow to the base of transistor than the transistor is switch on

followed by greater increase in collector current. The alarm

will switch on.

Modification/ Decision Making pg - 48

68. Suggest the modification need to be done to the circuit in
diagram below so that it can function as automatically fire
alarm switch that need high voltage.

Suggestion Explanation

Replace LDR with To detect heat when temperature

thermistor is high

Replace bulb with To produce sound

siren//bell

Connect relay switch to To switch on the siren

output transistor

Interchange the position To increase base voltage//voltage

of resistor R and across RI/base current

thermistor

Use 240 V power Siren is function as high voltage

supply

Modification/ Decision Making pg - 49

69. Modified the circuit 240V and Np = 4000 turns circuit to

switch on 12V d.c radio.

Suggestion Explanation

Step-down transformer reduce potential difference /

voltage

Ratio of turns 20 :1// Reduce potential difference 240V

240:12 Np = 4000 to 12V

turns and Ns = 200

turns

Using four diodes Full wave rectification

Using a capacitor To smooth out output current//

produce steady output current

Modification/ Decision Making pg - 50

70. Suggest and explain the safety ways, which are required

when handling radioactive substance.

Suggestion Explanation

Use thick lead box Radioactive rays cannot pass

through

Use forceps / robotic Avoid direct touch

hand

Wear photographic Able to detect exposure radiations

film

Wear plumbum safety To protect the body from expose to

suit radiation

Use siren Faster warning when leakage

Packed into concrete Prevent the radioactive waste

drum and buried discharge to environment

underground

Always place GM To detect the amount of radioactive

detector nearby nearby

Label the radioactive Easy to detect radioactive

container with symbol substance