KEWEI TAN
Essay questions Problem solving and decision making 1. INTRODUCTION TO PHYSICS Characteristics of instrument to measure diameter of ball bearing Consistency is higher The reading is more consistent Accuracy is higher Can give measurement closer to actual value Sensitivity Sensitivi ty is higher Can detect small changes in value to be measured Has no zero error To increase accuracy of reading. Every measurement must be minus with zero error Has no parallax error Eye must be perpendicular to the scale to avoid parallax error
2. FORCES AND MOTION MOTIO N Method to reduce the impact of impulsive force in egg’s drop competition from a height. (Mk) The egg’s casing Lengthen the time of made from soft impact material Use parachute To slow down the egg drop The egg’s casing Absorb the impact// part that hit the lengthen the time of ground when landing impact. made from easy to crumple material Characteristics of student to be in a basket ball team. (Phg) Mass is smaller More agile/ can change direction/increase direction/increase speed easily Taller Easy to shoot goal Responding time fast Easy to catch ball Powerful More energy/not tired easily Faster Can block/attack/run/defence faster Suitable characteristics of rope used for parachute. (Pls) Use a dynamic rope It is softer and could prevent injury. A lower density It is lighter Higher snapping Not easy to snap force A rope with smaller It will occupy less space. diameter Suggestion to design a water rocket. Made from tougher Not easy to break material Aerodynamic/streamline Reduce air friction shape Angle of launching is The rocket can travel
o
45 Amount of water is 1/3 of the whole volume Attached fins to the tail of the rocket
ery far To increase momentum and impulsive force Rocket can move smoothly and stable
Characteristics of the spring cradle Low spring constant Less stiffer and the spring can oscillate with low frequency Low density Small mass and lighter Low rusting rate Not easy to rust and lasts longer. Two springs are Can withstand a heavier arrange in parallel baby Put string in the To prevent the baby from spring falling down in case if the spring breaks Explain safety features of the car. Safety belts. To prevent the passengers from being thrown forward due to the inertia when accident occurs. Air bags Cushion the passengers from direct impact with the steering when accident occurs to reduce the impulsive force. Easy crumpled To reduce reduce impu impulsi lsi e force. force. steering. Front and rear To extend time of impact crumple zone. so that the impulsive force will be reduced. Use stronger spring To reduce vibration when for the suspension the car being used off road system Anti-scattering ill not harm the windscreen passengers and driver when it breaks. Head rest To keep the position of head when the car being hit from back. Passenger safety To prevent the car from steel cage/cell built being crumpled when it is from reinforced steel overturned. ay so that the pole vaulter can jump higher and lands safer. Run faster Increase the kinetic energy Use elastic pole Produce higher elastic potential energy Use tight sport wear Reduce air friction Use thick mattress Increase the interval of with soft surface impact on landing, thus reduce the resultant impulsive force Landing on the back Increase the surface area and reduce pressure Use a spike To run faster and increase kinetic energy Modify a normal car into a racing car. Use of higher power To produce high thrust engine force Use of strong ill not break/damage composite material easily Use of engine which ill not damage at high is able to withstand temperature high temperature Use of low density To have smaller mass material
Aerodynamic shaped Use of spoilers at front, rear and side of the car
Use of wider tires Use of hydraulic brakes Center of gravity of the car is lower Additional safety belt
Improve the safety steel cage/cell with more reinforced steel
To reduce air resistance To create a downward pressure (Bernoulli’s effect) to prevent the car from being lifted upward at high velocity To produce better grip to the road So that the car can be stopped faster To increase the stability of car To prevent the driver being thrown forward during collision. To prevent the car from being crumpled when it is overturned.
Method so the pole vault athlete can jump higher and safer. Bend the body when To reduce the air friction running to take off. so that the acceleration will be greater. ear tight clothes To reduce air resistance Use spiked shoes To give stronger grip for greater speeding Pole is made from The potential elastic soft but stiff material energy is high thus the height of jumping can be increased Pole is made from ill not break easily tougher material Put soft and thick To increase the time of mattress on the impact and reduce the landing pit impulsive force Land on the back Increase the surface area and decreases the pressure inverted. Design of the water rocket so that it can fly further and faster. High volume / mass Can increase the of water momentum to the back thus increase the explosive force Soft drink bottle Decrease the mass and increase the explosive force Add wing on the Rocket fly in stable bottle Add something to Reduce the air resistance the part of the bottle to make it sharp and aerodynamic Add weight to the Rocket can move straightly st head of the rocket and the head move 1 Use a higher power Pushing force to the back pump is high, momentum to the back is high Flying degree is 45 The flying distance is degree longer Modify the ordinary motorcycle to become a racing motorcycle Use softer and wider To strengthen the grip of tires the tires on the road Use an aerodynamic To reduce the air shape resistance Low center of gravity To make it more stable Made from low More lighter and can density materials increase the acceleration.
Use heavy engine and place it in the middle of the motorcycle Use powerful engine Use front and rear disc brakes
The motorcycle is more stable
To produce high thrust force. So that he motorcycle can be stopped easily.
Design of the safety belts ider Large surface area will reduce pressure to the driver/passenger Can be expanded To reduce impulsive force Made from tougher Does not break easily material Made from non-stiff So it is soft and material comfortable to use Design of the satellite that falling back to the earth so that it is not damage. Made from material Not easily become hot. that has higher specific heat capacity Aerodynamic shape To reduce air resistance Protected by a good To prevent the heat heat insulator reach/enter the inner part of the satellite Made from low The mass will be smaller density material so the impulsive force is reduced Made from tougher Not break easily material Attached with To reduce the velocity parachutes Attached with So that the satelite is not cooling system become hot/melt easily Design of springs for athlete’s exercise purposes Parallel arrangement To increase the stiffness of the spring. Short in length To reduce the extension of the spring. Small in diameter Greater force is required to stretch the springs. Covered with plastic. ill not harm the athlete if the springs are broken. Made from nonCan be used for a longer rusting materials. time/durable. Fix with holder at the Can be easily be held and end of the spring stretched Fix an elastic rope in To prevent the springs the springs from being stretched over it’s elasticity limit. Modification to the bus to improve the safety of the passengers. Attach safety belts. To prevent the passengers from being thrown forward due to the inertia when accident occurs. Air bags Cushion the passengers from direct impact with the front seat when accident occurs to reduce the impulsive force. Front and rear To extend time of impact crumple zone. so that the impulsive force will be reduced. Use stronger spring To reduce vibration when for the suspension the car being used off road
system Shatter proof windscreen and window panels Head rest
Passenger safety steel cage/cell built from reinforced steel The bus is made from tougher material
Break into small pieces with blunt edges and will not harm the passengers. To keep the position of head when the car being hit from back. To prevent the bus from being crumpled/collapsed when it is overturned. To avoid the bus being dented when involved in accident
Characteristic of spring to be used as a spring cradle. (Ktn) Springs are arranged Can support higher load. in parallel Use stiffer spring Not easily broken/ spring constant is higher. Stainless steel Can be used for longer time. Shorter spring Spring constant is higher/stiffer. Characteristics of arm exercise equipment made from spring that is suitable to use (J) Spring made from Can be used for longer stainless steel time. Made from steel The spring is stiffer Spring made from ire not break easily thicker wire Spring with smaller Can withstand bigger diameter force, more stiffer Modification of a fisherman boat so it can be used for deep-sea fishing. (MRSM) Shape of the boat is Less water friction. streamlined Made from tougher Can withstand big wave material Stainless steel Can be used for longer time. Less maintenance Use ultrasonic wave More energy and can penetrate deeper in the sea Bigger cool room Can put a large amount of fish for longer time. Suitable characteristics of tractor used to do heavy works Use larger tires Larger contact area produces low pressure and the tractor will not sink into the ground Larger mass Larger inertia Low centre of gravity More stability Use liquid in the Liquid cannot be hydraulic system compressed Characteristics of spring to be used as the motorcycle spring Smaller diameter of Enough space to place the spring spring to the motorcycle. Higher elastic limit Can support more load Higher spring Small compression of the constant spring due to bigger load Smaller natural To reduce bumping effect frequency
Essay questions Problem solving and decision making 3. FORCES AND PRESSURE Specification of watercraft/ship. Cross sectional – Reduce water resistance. Front side narrow and pointed Hull made from Lighter, stronger and not aluminum corrode. Hydrodynamic ithstand shock waves. shape. Reduce water resistance (Stream-lined) Diesel engine Cheaper and powerful Specification of submarine. (MRSM) Use nuclear energy Can be used for longer time Use ballast tank Can float and submerge easily Fix with periscope Can look at the surface of the sea without floating on the surface Use ultrasonic wave Can penetrate further for radar Characteristic of ship that can carry heavy loads. (SBP) Streamlined shape Reduce water resistance Made from high Able to withstand bigger strength metal wave Ship base cross Abele to displace out more sectional is wider water to gain more buoyant force olume of the air Can displace out more space in ship is water//increase the volume bigger so overall density is lower than water Characteristics of hydraulic brake. has a high specific Plate not easily heat up heat capacity High boiling point Not easily boil at high temperature Fluid that Pressure can be transfer uniformly to whole the fluid Use non-corrosive To not destroy the brake fluid system Brake made up of Not easily get rust stainless steel Design of a buo on the sea surface Painted with bright Can be easily seen in the color morning and at night Fix lamps on the Can be easily spotted at buoy night Made of thick and ill not easily split and hollow material waterlogged Fix small flags on the Can be easily split and buoy waterlogged Tied with ropes to To prevent the float from the seabed sweeping away Not made from metal To prevent the float from rusting and can be used for a long time. Hollow and big in To have buo ancy and size floats
Modification of a pesticide sprayer into painter sprayer. Use a compressor Provide high air pressure with high ac voltage. continuously. Use compressor To give high air pressure which produce high and produce stronger pressure. spray. Made from low Light and can be bring to density materials anyway Use materials that Do not rust/corrode easily resist to and last longer. corrosion/rusting. Use stronger Do not easily broken or materials damaged Use a bigger paint Enable to store more paint. container. Adjustable nozzle Can control the size of the sprayer. spray. Use longer nozzle Can spray the hidden part. spray. Design for the water tank to store a large amount of water Made from Makes the tank stronger composite materials and does not break easily and fiber Made from low More lighter density materials Thick wall at the To enable the water ank to bottom of the tank withstand the large water pressure at the base of the tank The water tank is So that the tank will not placed on the thick sink into the ground concrete floor Large tank base To reduce pressure and prevent the tank from sinking into the ground Build the water tank To increase the pressure of at higher placed/ the water build a tall design Build larger water Can stored more water tank Modification to the hydraulic jack to enable it to lift mass of greater quantity Use piston of bigger Can support greater force cross-sectional area (weight) Use low density ery light and easy to carry material Non-compressible Piston can be lifted up liquid Longer handle Less effort needed to press the small piston. Apply released valve Liquid can flows into small between small and reservoir. main reservoir. Use stronger metal Not easily broken. Use non-corrosive ill not corrode metal and liquid long lasting. Characteristic of an automatic tennis ball shooter. Small spring To ensure hat the elastic diameter potential energy is higher. Thicker spring wires So that spring constant is higher/more elastic/ball can be shot out at a high velocity. More number of So that the compression spring coils length is l onger. Low density of tennis To ensure that it moves ball is used faster and further.
Suitable characteristics of a wings to be installed with the body of the aircraft A shape of crossTo produce the speed of air section which is flow above the wings to be upper side is longer higher than the bottom than the bottom area. The area of the wing To produce larger lift force is larger Made from low Less weight//very light// to density material. produce more upward resultant force. The difference in To produce higher speed of air is higher difference in pressure Design of the astronaut’s suit hite color/shinning To reflect the cosmic ray Made from tougher Not easily torn material Made from non-stiff So that the astronaut can material move easily. Lined with To avoid the penetration of lead/plumbum radioactive radiation. Use photographic To check the exposure to badge. the radioactive radiation of the astronaut. Put on safety space To allow the astronaut to helmet made from look at his surroundings. tough glass Modification of hydraulic jet to overcome bigger force Increase the surface area of bigger cylinder Decrease the smaller surface area of the cylinder Hydraulic oil that will not evaporate easily Larger base area of hydraulic jet Made from harder alloy Made from low rusting effect object
Can easily push up bigger mass object Can push up bigger mass with lesser force Not easily evaporated when in high temperature More stable Not easily break when supporting bigger mass object Can use for longer period
ay to increase the cleaning efficiency of cloth. Use detergent Remove the dirt and moistening the cloth Use hot water Decrease the surface tension of the water and moistening the cloth. Use automatic Can control the amount of mashing machine water being used Use pipe water (soft Enable the soap to form water) not well water scum and increase the (hard water) cleaning efficiency Clothes are made To avoid the oil and dust from materials that stick on the clothes can decrease the stickness between the clothes and the dirt aterproof clothing So that the clothes will not become wet when we sweat Use more efficient Clothes will be shivered washing machine along with the detergents to remove the dirt Use computerized Can control the washing machine usage/volume of water
Suitable characteristic of hydrometer to measure the density of concentrated acids. Material made from Glass does not corrode glass with acid Small diameter of To increase the sensitivity capillary tube of the hydrometer High density of shots Makes the hydrometer stays upright Big diameter of To obtaine bigger upthrust bottom bulb force so the hydrometer can float Suitable characteristics a boat Streamlined (larus) in shape Lower density material Higher specific heat capacity High strength Corrosion effect is lower
of metal to be used to built To reduce water resistance It will be l ighter. Absorbs more heat but become hot slowly Not easy to damage Not easy to rust/corrode.
Modification of the balloon so that the balloon can float and carry more passenger and has safety features for the passenger Use hot air/ Less dense than the helium/hydrogen gas atmosphere//lighter Larger basket Can bring more passengers Balloon/basket made To reduce it weight from low density material Basket fit with Comfortable and reduce cushion impulsive force when landing Use burner To control the height of the balloon by producing hot air. Equipped with Can be used to save the parachute passengers if the balloon is not functional. Equipped with safety To avoid passengers from belts fall down. Suggestion to built a barge (tongkang) that can carry heavy load, faster and safer Built from stronger Can withstand great force material Lower density Lightweight material Has two stage Save in fresh and salt plimsoll line water Bigger size Can place more load StreamlinedReduce water friction aerodynamic shape Specification of component in the brake system Disc brake is made Not easy to become hot from higher specific heat capacity material Higher melting point Not easy to melt at high of brake disc temperature Compression of Difficult. brake liquid Higher hardness of Can be used for longer brake disc time.
Characteristics of fluid/liquid used as a hydraulic fluid Higher boiling point Not easy to boil at high temperature Higher specific heat Not easy to become hot capacity Lower density So the hydraulic jack will not become too heavy Has lower rate of No easy o expand so the expansion volume will be constant Design of hydrometer use to measure the density of an acid solution. Smaller and longer Increase the sensitivity stem. where the scale divisions are far apart so that small changes in density can be detected. Use glass to built the Do not erode and small hydrometer adhesive force. Larger diameter of Higher up hrust bulb force/displaces more liquid/able to float easily Use lead shot in the Hydrometer can float bulb vertically and stable. Suitable characteristic of hot air balloon which is able to carry more passengers to a higher altitude in shorter time. Larger balloon size To produce bigger bouyant force. Use many burners To produce bigger flame. Heat up the gas in shorter time. Use synthetic nylon Lighter, strong and airproof Higher temperature Reduce the density of the of air in the balloon air in the ballon.
Essay questions Problem solving and decision making 4. HEAT Characteristics of an ice cream container. Use low specific heat Easy to get cold//become capacity to bulit cool easily. inner box. Smaller size of ice Easy to carry because it is cream box lighter.//Easy to become cool. Outer box is made It is poor conductor// It is a from PVC plastics good heat insulator. Outer box colour is Does not absorb heat from brighter. surrounding quickly. Has gap between Avoid heat from inner box and outer surrounding enter the inner box and fill with heat box. insulator. Suggest the suitability of material used to determine the specific heat capacity of aluminum Put on asbestos A good heat insulator. Avoid heat loss by conduction. rapped with tissue Avoid heat loss by paper radiation/ to the surrounding Put some oil in the Better heat contact hole between aluminum block and thermometer. Higher power Can increase the immersion heater temperature faster. Characteristi c of spatula use as a kitchen utensil (Mk) Shape of the handle Easy to handle is slim Density is lower Its is lighter Higher melting point Not easily melt at higher temperature. Higher specific heat Not easily become hot. capacity Desing of the ice container. Lower density Smaller mass, lighter and easy to carry. Higher specific heat The container is not easy capacity to become hot/cold Made from good heat To avoid heat from insulator surrounding enter the container. Shining surface. To reflect the heat from surrounding and avoid the heat being absorbed by the container. Put a cover to the To avoid heat from enter container. the container.
Design of the car radiator Use water as a Higher specific heat cooling agent capacity Use bigger fan Can sucked out more heat from the radiator Use water pump To help in the flow of water to the radiator Paint the radiator Black body can radiate with black paint more heat Number of cooling Cooling will be more fin is greater efficient Characteristic of a school’s physics laboratory thermometer. (MRSM) Bulb is smaller More sensitive Rod is thicker Stronger, not easily break. all of the bulb is Allow good heat thinner conduction Capillary tube bore is More sensitive, more smaller accurate reading Use mercury Opaque and can be seen easily Do not stick the glass Rod is longer ider range of scale and more sensitive Suitable characteristics of the solar cooker Use concave mirror Use spherical concave mirror
Kettle is made from metal The kettle holder is made from insulator
ill converges all light to the focal point ill converges more light to the focal point hence increases the intensity of light/heat Metal is good conductor. Easy to handle the kettle and not so hot
Modify/design of an efficient solar water-heating system. Use insulator behind To prevent the loss of the absorber panel heat energy Use an absorber A black surface is a good panel which is absorber of radiation so it painted black. will absorb heat faster The pipe inside the Metal is a good heat plate must be made conductor, of metal so it will transmit heat to water easily Pipe embedded in Longer pipe will enlarge plate must be long surface area will absorbs heat faster Use glass cover on To trap heat energy. the top of the panel (energy is radiated in, but cannot radiate out again). Design of the oven so that the oven will use less electricity and user friendly Fix a bulb in the oven Can see the cake clearly Has stand so the So the user can load and oven is at eye level unload the cake easily. Built the oven so that Can bake large amount of the oven has many cake in one time. racks Insulate the oven The heats will not loss to with good heat the surroundings. insulator
Fit with a glass window to the cover. Fit a fan in the oven Made from stainless steel
Can see the cake without opening the cover. So the heat will spread uniformly in the oven. Last longer/durable.
Design of the hot food container. Lower density Smaller mass, lighter and easy to carry Higher melting point Not melt easily at high temperature Higher specific heat Not become hot easily capacity Lower heat To avoid loss of heat to the conductivity surrounding. Design of a cooking pot Pot made from lower specific heat capacity material Lower rate of corrosion. Made from lower density material Made from aluminum Handle is made from higher specific heat capacity.
Easy to become hot with small amount of heat. Not easy to corrode and does not contaminate the food The mass will be lower and easy to handle Lower density and cheaper. Not easy to become hot.
Characteristics of hot water tank. High specific - To ensure that it will not heat heat capacity up fast. Low density - So that its mass is smaller and easier to be managed. Low rate of - So that it will not be easily oxidation oxidized / rust when contacts with hot water. Durable - To ensure that the reservoir will not break easily when it is filled with large amount hot water. Characteristics of liquid use as a cooling agent for engine. Specific heat Not easily become hot capacity must be high High boiling point Not easily boiled in high temperature Ph7 ill not corrode the engine rusting low ill not caused the engine to rust Characteristics of car radiator use to cool the engine. Large number of To ensure that more amount cooling fins of heat is released at a short period of time. Size of the fan is So that the radiator can be big cooled quickly./ Direct large amount of air to the radiator. Use water Specific heat capacity of water is high and takes time to become hot. Use cover with To ensure that pressure in the spring radiator can be release automatically.
Suitable characteristic of metal to be used as a cooling fins of a motorcycle Lower specific heat Easy to get hot or cold of capacity Higher melting point Does not melt easily Good heat conductor The heat can be lost easily Lower rate of The shape of in unchange expansion
Essay questions Problem solving a d decision making 5. LIGHT How to build a compound microscope . Eyepiece – use longer focal length f e Objective lens – use shorter focal length. = f o f e > f o Label the f e and f o Draw a ray diagram to show the or ation of images. Ray diagram • • •
Suggest suitable modification o increase the efficiency of compound micro cope. (Ktn) Eye piece has longer Has higher magnification focal length than actor. objective lens. Object is place To produce real, magnified between f o and 2f o and in erted image Adjusted so that To act as a magnifying object for eyepiece is glass place u f 0 + f e rom t e eyepiece. Store in cool and dry To av id the formation of place ungu .
• •
Design an optical instrument i the double-decker bus so that The driver at the lower deck is able to see the upper deck. With chea er cost. (Phg) Use periscope Cheaper than CCTV 2 plane mirrors//2 Reflect light from object prisms Mirrors are arranged parallel li ht from first mirror will be reflected into second mirror Light from second m irror is re lected into the driver’s eyes Tube or casing to hold mirror asier to handle periscope o Mirrors are at 45 angle
How to built compound microscope. Thicker lens as an objective lens, thinner lens as an eyepiece. Fo and Fe are not overlapped. Light ray to form the first image. First image formed shown. Light ray to form final image. Final image formed shown. Diagram •
• • • • •
Explain how to built simple pe iscope and suggest modi fication to convert the periscope to binoculars
Draw a labeled diagram Specification of the optical fiber use i an endoscope for medical imaging.(Mk) Low density Lighter High flexibility Can be bent easily. High purity Avoid loss of signal. Smaller in size Can occupied in small space. Made from stronger Not easily break material Draw a labeled diagram
Use 2 right angle prisms Use eye piece and objective lens
The rays will ent through o 180 To magnified the image/ as a telescope
How you would build a simple binocul ar and suggest modification so the binocular will produced brighter and bigger image ( )
Objective lens with bigger diameter Eyepiece with bigger power
More light ca enter the binocular higher power as a magnif ing glass
Suitability of mirror use to watch over the shop costumer. (Pls) Concave mirror To provide wider field view Bigger size of mirror To enable a wider view and sharper imag . Hung the mirror at Easier to look /won’t disturb the top corner of the the costumer shop Characteristics of optical fiber Small critical angle Internal reflection can easily occur High density To have small critical angle Stiffness is low Can be easily bent High strength ill not break easily Small in diameter Does not occ pied much space Modify an astronomical telescope become a binocular. Astronomical telescope uses 2 con ex lens. Objective lens and eyepiece. Objective lens has longer f o. Eyepie e has shorter f e. Diagram •
•
Advantage of binocular Binocular is shorter//smaller in size. Easy to carry. Produced brighter image. • • •
Characteristics of lenses to built telescope. Objective lens with a Highe magnifying power long focal length Eyepiece with a short Highe magnifying power focal length Objective lens with a Enabl the light to enter big diameter and thus clearer the image o be een Eyepiece with a Suitable with our eye’s size small diameter and make it easier for us to see Design of fibre optics which c n work efficiently Use refractive index So that total internal of outer layer less reflection can happen in than the refractive he fibre optic. index of inner layer Use high flexibility So it can be bend material Use stronger Do no break easily material Use thin material Lighter/ can be used in small rea Low density material Lighte r Suitable characteristics of len to be used by a technician to repair watch. Use convex lens To magnify the image % of clarity is higher Image will be brighter and clearer Focal length is short To increase the power/to produ e bigger image/ image can be focused on he short distance Lens has smaller Easy to wear as a diameter spect cle. Suitable design for slide proje tor Use concave mirror. To reflect dan focus light to he slide Use two planoThe li ht from the source convex lens that will di tribute evenly to the have same power slide o that the image orme on the screen is bright r. The distance The i age formed on the between the slide scree will be magnified and the projection and real. lens is between f and 2f The slide would be So the image will be placed inverted uprigh t
Essay questions Problem solving and decision making 6. WAVES Suggest modification to built big hall so it is suitable for the assembly Bulit a dome shaped Improf the aqoustic effect or circular roof of sound/accomodate more student Increase the number Reduce effect of reflection of door. Built wall from To avoid disturbance from sound-proof material outside Inner wall made from To avoid reflection of soft material/use sound. cushion chair/curtain Placed l oudspeaker To produce more away to each other constructive interference region Increase the number To get sufficient amount of of light light. Suggest relevant steps to be taken to build a safe port for fishermen. Built the port at the The water wave is calmer gulf Built a wall that has a The sea wave will narrow gap in the undergoes diffraction and sea the amplitude will be reduced Built the wall using Not easily to collapse concrete Make small hole at To absorb the wave the wall energy. Built stronger wall To reflect the sea wave Built higher wall The sea wave cannot pass through over the wall The wall must be So that the wavelength can slanting be reduce when the sea wave hit the wall Characteristics of waves which are use to determine the depth of the sea. High frequency Higher energy and enable sound wave the wave to travel further Higher amplitude High energy and enable the wave to send to further places Higher percentage of So the reflected signal can energy reflected from be detected easily seabed Rate of sound So that the wave can be absorption by the easily reflected and water is low detected by the hydrophone.
Suggestion to built beach resort Built at bay ater is calmer. Sea is shallower Built retaining wall Reflected back the wave to open sea. Built gap in the wall Diffraction occurs. Energy of wave is smaller Higher wall The wave cannot passed over the wall all is built using The wall will be stronger. concrete Characteristics of wave use to detect a school of fish Longitudinal wave. Sonar sound is longitudinal wave Higher frequency Has higher energy Higher speed Can travel faster in the sea Higher penetrating Can penetrate through power medium easily
Essay questions Problem solving and decision making 7. ELECTRICITY Suggestions of material used to build heating element. Lower density Light weight Higher melting point Not easy to melt at high temperature Low rate of oxidation Can be used for longer time. Lower surface area. Resistance will be higher and produced more heat. Used longer wire Higher resistance and can produced more heat Design of pylon for transmission of electricity. (Phg) Use step up Current will be smaller and transformer to less loss of energy increase the voltage before transmission process Use low resistance Less loss of energy to wire overcome the resistance Use low density wire Lighter. Easy to hung on pylon. Higher pylon For safety purpose. Not reach by others Tougher material to Not easy to collaspe build pylon. Steel alloy U shape steel alloy Not too heavy Large diameter cable Less resistance
Characteristi cs of power socket extension for normal use. (MRSM) Not using extension Less resistance, less loss cord// use shorter of energy as heat energy extension wire One fuse for each If one fuse blow the other socket can still function Use power surge Can cut off the supply protector. when it is overloaded Head plug earthed Flow current leakage to earth Suggestion to light up a room. (Pls) Use fluorescent lamp Consume less energy Use more efficient Brighter and prevent fluorescent lamp. wastage of energy. Use fuse To prevent overheating of lamp. Two or more If one lamp blow out, the fluorescent lamp is other can still function. connected in parallel
Specifications of lamp that is suitable to use as a reading lamp. (J) Low power rating Consume less electrical energy Low cost Save money//cheaper High efficiency Produced higher output power // less energy wasted Long lifetime Last longer Suitable design for wiring a cabin. The electric Allow each electric appliances are appliances to be switched connected in on and off independently parallel//diagram Fit fuse at the live To stop the flow of current wire in the fuse box by melting when a high //diagram// voltage of electric current Use miniature circuit flows through the circuit // breakers (mcb’s) 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 Use thicker wire Use insulated wire Place the power point at higher place
To save the energy
Reduce resistance To avoid short circuit To avoid being touch by the children
Modification to the desk lamp so it is comfortable to use Use a fluorescent Fluorescent lamp use less lamp electrical energy Use bigger cover Reduce light directly with white color propagate to eye and reflection and reflector light and heat energy Use an adjustable Height of the lamp can be stand adjusted and can be used anywhere Connect with earth Flow the current leakage to wire the earth Use an energy saver Use same amount of lamp energy but light up brighter Characteristic of connecting wire Resistance of wire is To prevent power loss due low to heat Melting point is Prevent wire from melting higher at high temperature Density of wire is low So it is light weight and reduce the mass Rate of rusting is low Prevent the wire from rusting and can be use for longer time Lower rate of To prevent lengthening of expansion wire
Specification of wire used for heating element Lower density The mass is smaller and light weight Higher melting point ill not melt easily at high temperature Lower oxidation rate Can be used for longer time Higher resistance Produce more heat energy Modification to the circuit to improve safety, produce the lamps light up with normal brightness and increases the efficiency of electrical energy consuming Attach one fuse to To break off the circuit the live wire in the when large current flow consumer unit and produce fire Use an insulated wire To prevent short circuit Use thicker wire To reduce resistance and improve efficiency. Attach switch for To allow each lamp to be each lamp switched on and off independently Connect the metal To flow electron (extra) to fitting lamp to the earth and avoid electric earth wire shock. Using only 240 V To ensure the bulbs light light bulb up with normal brightness Connect the bulbs in Each bulbs will receive parallel same voltage Suitable characteristics heater Smaller surface area/diameter High melting point Low specific heat capacity Long coiled metal
of metal to make a water The resistance will be higher Not easy to melt The temperature rise slowly To increase the resistance.
Characteristics of metal use as a heater. In electrical kettle. High resistance Higher resistance make the heating better High melting point Not easily melt in high temperature Low rusting effect Not easily to rust n safe for consumer Low specific heat Easily 2 become hot capacity Characteristics of the current distributor cable in the car. Low resistance A little energy is lost as heat energy Low density Small mass and easy to be carried/hung ire with large To reduce the resistance diameter Low expand rate Does not contract too much and becomes too loose during hot days.
Suggest modifications that can be made to the electric kettle so that it can boil water faster and has better safety Diameter of Less resistance and connecting wire is produce small amount of bigger heat. If large current flow the wire will no be overheated Length of connecting Less resistance wire is shorter Heating element Can produced high amount must have high of heat energy with smaller resistivity current The kettle is made Less heat loss to from good heat surounding. Water will boil insulator faster Use suitable fuse. If If higher current flow the the current flow is fuse will melt and kettle will 8.3A. Use 13A fuse no be damaged cartridge
Essay questions Problem solving and decision making 8. ELECTROMAGNETISM Modification to enable moving coil microphone o detect sound effectively and generate bigger current. Use thin diaphragm Easy to vibrate. Use stronger Not easy to break. material to built diaphragm Use more number of Increase the rate of change turns of coil of magnetic flux. User thicker wire To reduce the resistance of wire. Use powerful magnet To increase the rate of to has stronger change of magnetic flux. magnetic field Suggestion to make a hand phone charger (Phg) Use step down Able to reduce voltage transformer from 240V to 9V Use a diode Change ac to dc Use capacitor Able to smooth the output current. Suggest modification so that the galvanometer can increase its sensitivity. (J) Increase the strength Increase the force between of the magnetic field current carrying conductor and the magnetic field. Using lower stiffness Smaller opposing force to of hairspring stop the turning of the coil Lighter mass of coil Smaller inertia, able to move easily. Increase the area of More change to the the coil magnetic flux, a bigger force is produced. Design of a moving coil ammeter that can function better(Mk) Use stronger magnet Stronger magnetic field/ large rotation Use curve magnet Produce radial magnetic field Use cylindrical core To supply uniform magnetic field strength Use soft iron core To concentrate the magnetic field Use linear scale The angle of rotation is linear and more accurate Design of the ac generator so that the efficiency of the generator is higher. Use soft iron core To concentrate the magnetic flux Increase no of turns To increase the rate of of coil magnetic fluxs cutting Use bigger/thicker To reduce resistance of the wire wire Use curve permanent So rate of the rotation and magnet magnetic fluxs cutting is constant Use powerful To increase the rate of permanent magnet magnetic fluxs change
Suggest modification to ac generator to that can produce bigger dc current. (Ktn) Increase the number Increase the rate of cutting of turn of coil the magnetic field Use stronger magnet Increase the strength of the magnetic flux Use curve magnet To provide radial magnetic field Diameter of wire of Thicker wire has lower coil is greater resistance. Higher current can flow. Use copper wire Lower resistance. More current flow. Suitable characteristics of electric bell that can produces a louder sound Use bigger hammer So that the surface area contact is bigger/produce more impulsive force Distance between the The force applied to the hammer and the gong is larger gong is larger Number of turns of The strength of the the coil is l arger magnetism is higher High curvature of the The area of air molecule gong vibrate is greater. Modification to be done to enable the electric bell to ring louder Increase the number Produced greater magnetic of turns of wire field to produce greater force. Increase the To increase the resultant of magnitude of the magnetic field current/ the number of cells Used u-shape soft Produced stronger iron core magnetic field Use bigger diameter ill vibrate more air of the gong molecules Use bigger hammer Produces greater impulsive force. Advantage of the National Grid Network Cost of generation of electricity is reduced
Electricity supply is more reliable with less interruption. The generation of electricity at each station can be controlled and regulated Power station can be located outside the city limits.
Because high voltage reduces the current flow. Reduces power loss in the cable. Because repair and maintenance work can be carried at any power station and at any time. At peak hours more generators can be switched on.
So that air an environmental pollution can be reduced.
Suitable characteristics of materials to be used as a model of power transmission. Use 12V ac power Can be change the voltage supply with transformer Use laminated soft Produced stronger iron core magnet// easy to magnetize and to demagnetized Use step-up To increase and to transformer Np= decrease the voltage due 1200, Ns=2400 and to the demand/need. step-down transformer with Np=480 and Ns= 120 Use copper wire Lower resistance. Suitable characteristics of cables use as a transmission cable. 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 The cables will not expand expansion under hot weather Modification of the loudspeaker to produce louder sound. Increase the number To increase the magnetic of turns of coil field strength/ current produced Use larger diameter Reduce resistance in the of wire coil Cone made from Easy to vibrate lighter material Use stronger magnet Cone will vibrate stronger and produced more emf. Bigger diaphragm ill vibrate more air to produce louder Cone made from Not easy to break. tougher material Suitable characteristics of the hand phone charger. Connect the output with a diode Connect capacitor Use the primary turns and secondary turns with the ratio 2:1 Use soft iron core
Use laminated iron core ound the secondary coil the primary coil or placed very closed to the primary coil(along the same core) Use wire with low resistance Use full wave rectification circuit
To change a.c. current to d.c. current Smoothen the a.c. current Reduce the current to become 12V
Can me magnetized n demagnetized easily and reduce the energy lost Increase the resistance to the flow of eddy current Prevent leakage of magnetic flux
Reduce energy lost To reduce loss of energy
Modification of transformer to become a step-down transformer with 12V dc output. Connect the output with To change a.c. current a diode to d.c. current Connect capacitor Smoothen the a.c. current Use the primary turns Reduce the current to and secondary turns become 12V with the ratio 2:1 Use soft iron core Can me magnetized n demagnetized easily and reduce the energy lost Use laminated iron core Increase the resistance to the flow of eddy current ound the secondary Prevent leakage of coil the primary coil or magnetic flux placed very closed to the primary coil(along the same core) Use wire with low Reduce energy lost resistance Characteristics of cable to be used in the National Grid Network. Larger diameter To reduce the resistance of wire Lower density The cable will be lighter and can be supported securely The rate of So there is less expansion expansion is low and less sagging in the cable during hot day. Higher melting point Cable does not melting in high temperature. Problem Involving electricity Transmission Cost of cable. Aluminum cables are used because the density is lower (the cables become lighter), have low resistance and cheaper. Loss of power by By using thicker the cables aluminum cables, resistance can be reduced By using a high voltage transmission, the current in the cables is reduced and the power dissipated by the cables is reduced. Charge leakage To prevent charge between the cables leakage, the aluminum and the earth cables are supported by high metal tower/pylons. The metal support of the tower is earthed so that it is safe for the worker or public. •
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Suggestions to design a moving coil loudspeaker that can produce louder sound. Use radial shape of The magnetic field strength magnet is uniform. Coil is built To increase the surrounding the effectiveness of the magnet//Attached to counter react between the the magnet magnetic field. Used lighter material Can easily vibrate. to built diaphragm Use ac power Audio signal varies with the current. Box made from Loudspeaker is stronger. wood/steel ay to build a industrial lifting electromagnets. Large number of Increase the turns of coil electromagnetic strength Use soft iron core Can be magnetized and demagnetized easily Insulated copper Prevent short circuit wire Use higher To produce a strong voltage/current magnetic field Use thicker wire To reduce the resistance of the coil Design a circuit that can be used to switch on 12V dc radio Use step-down Capable to reducing transformer potential difference/voltage The ratio of no of Can reduce 240V to 12V turn of primary coil to secondary coil must be 20:1 Using four diodes Full wave rectificati on Using capacitor To smooth out output current//produce output of steady dc Suggest modification to the dc motor to increase the efficiency of the motor. Increase the strength To increase the magnetic of the magnet field strength. Increase the number To increase the magnitude of turns of coil of force Increase the To increase the magnitude magnitude of current of force/ increase the strength of the magnetic field. Characteristics of dc motor that can be used to lift heavy object. Lower density Coil has smaller material mass/lighter Higher number of Larger force acting on the turns of coil coil. Higher electromagnetic field strength Stronger magnet Large force acting on the coil More number of Coil rotate smoothly segment in the commutator
Essay questions Problem solving and decision making 9. ELECTRONICS Characteristics of circuit with transistor which is used for fire alarm system. Negative terminal of cell is connected to the emitter/ Positive terminal of cell is connected to the collector of transistor. Heat Dependent Resistor (HDR) is placed on top while resistor R is placed at the bottom. Resistor Y is placed at the base of transistor.
Connects extra components such as siren/bell and light. Use AC current in the outer circuit to switch on the siren.
- So that forward biased occurs - Current can flows through the transistor
- So that when there is a rise in temperature, voltage across X will be higher. - Base current will flow. - To limit the amount of current that passes through the transistor./ To protect the transistor from any damage. - So that sound or signal is produced during fire.
- The larger is the AC current, the louder the is the siren.
Draws the fire alarm system with electromagnetic relay at the outer circuit and uses AC current to switch on the siren
Essay questions Problem solving and decision making 10. RADIOACTIVITY Characteristics of radioisotope to be used to inject into the blood of a patient to detect the location of a brain tumor Shorter half life Can be active in the body for shorter period. Lower ionizing power Causes minimum damage to the tissues in the body Emit gamma ray Can penetrate through the body and detected by the GM tube Characteristics of radioisotope to be use to detect the level of juice in a bottle Longer half life Can be used for longer time Beta ray Can be absorbed and medium penetrating power Solid Easy to handle Ionizing power is Not ionize the juice. Safe to low. drink. Suitable characteristics lighting arrestor. (Pls) Solid state Higher ionizing power
Longer half life
of radioactive to put on the Easy to handle Easy for the medium to conduct electricity and cause the lightning to divert to the place of higher ionization. Can be used for longer time.
Characteristic of radioisotope to detect the thickness of paper in a paper industry. (Ktn) Solid Easy to handle Emit beta ray Medium penetration/ can be absorbed. Longer half life Can be used for longer time. Medium penetrating Less dangerous power Characteristic of radioactive use to detect the water pipe l eakage.(J) Emit gamma Penetrating power is high and can penetrate through pipe and soil. Shorter half life. Active in water supply for shorter time. Liquid Can be dissolved in water easily. Characteristic of radioisotope use to detect problem organ/blood circulation (Mk) Shorter half life Active in the body for shorter time Lower ionizing power Minimize the damage to the organ. Gamma ray Higher penetrating power/can be detected. Liquid Can be dissolved easily
Characteristic of radioisotope use to kill cancerous cell. (radiotherapy) (Mk) Long half life Can be used for longer time Lower ionizing power Minimize the damage to the organ. Gamma ray Higher penetrating power/can be detected. Solid Can be handle easily Explain the suitability of radioactive source to be use to kill cancer cell Can produced gamma Higher penetrating power ray Longer half-life Can be used for longer time Solid Easy to handle Lower ionizing power Do not cause cell mutation Suggest how the radioactive material and the detector should be chosen to be use in the study of the intake of fertilizer. Shorter half life – a This allow time for the few days. fertilizer to be absorbed Use GM tube to The location of the ertilizer detect the radiation can be detected and analyzed. Characteristics of paper thickness control device using radioactive Half life of - So that it can be used for radioactive a long time./ Does not have substance is long. to be changed often. Radioactive substances that release Beta particles Solid Radioactive substances Use GM tube GM tube is placed opposite of the radioactive source. Papers are placed at the centre of GM tube and radioactive source.
- Moderate penetrating force.
- Easy to handle and manage. - Can detect Beta particles. - So that the intensity of Beta particles can be detected. - So that the Beta particles can penetrate the papers and detected by GM tube.
Suggestion and explanation how to detect the presence of blockages in the blood vessel using radioisotope as a tracer Use a small amount Can emit γ, and can of Natriumpenetrate through the 24//Thaliumpatient’s body 201//Technetium-99 Has short half-life ( a Not pose any serious few days) health risk due to overexpose to the radiation Use GM tube as a Can detect γ ray. detector The radioisotope is Can flow to the entire body injected to the blood of the patient. vessel Radiation from the Identify the region that is radioisotope is not receiving enough detected with GM blood. tube -Higher reading means blockages. -Lower reading mean the region is receiving not enough blood. Suitable characteristics of radioactive radiation and detector used to detect the underground water supply leakage The radioactive Can penetrate the soil and source emit beta emerge from the ground particles Shorter/sufficiently After the period of two long half life days the activity of the source is weak enough and not dangerous Use GM tube as a ery sensitive, can detec detector beta particle and easy to carry from one place to another Use a rate meter Can give the count rate directly Suggestions to modify your school lab with well equip which can be used to do the research work for radioactive source safely Use thick lead box as Radioactive rays cannot a radioactive source pass through container Radioactive waste is Prevent the radioactive packed into stainless waste discharged to the steel /concrete drum environment and buried underground Use forceps/robotic Avoid direct touching hand Use siren Faster warning when leakage Characteristics of radioisotopes that are suitable for use in controlling the population of pest Use solid Easy to handle. radioisotope Can emit gamma ray Has higher penetrating power. Has longer half-life Last longer
