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Key info: 6 marker- variables,equipment,equations,safety Bar chart-discontinous (categoric data) Line graph-continuous data How can we measure accurately with measuring cylinder โ Reading taken at eye level,from bottom of meniscus โ Ensure measuring cylinder is empty,on horizontal surface ALWAYS USE EQUATION IN EXPLAINING QUESTION HOW TO ANSWER 4 MARKER DATA FROM GRAPH: โ Use two data points โ Evaluate both of these โ Reach conclusion Graph relationships: Linear-straight line Note-in order to be proportional,line must go through origin
Forces and Motion
The parachute jumper opens her parachute at point B. Her velocity decreases until she reaches terminal velocity again at point C. Explain this change in velocity (4) โ Air resistance increased when parachute opened โ Air resistance greater than weight โ Deceleration โ Air resistance decreases with speed โ Resultant force becomes 0 โ Constant speed Type of distance Factors Thinking distance โ Tiredness โ Age โ alcohol โ drug use Braking distance โ Mass of car โ Tyre conditions โ Road conditions Vector โ Velocity โ Displacement โ Acceleration โ momentum Scalar โ Speed โ Distance What is meant by elastic behavior? โ idea that material returns to its original shape / length; โ when the load / force is removed; What happens when a car hits a block โ Increases time of collision โ Less acceleration Explain how a student can investigate if the spring obeys Hooke's law
Advantage Disadvantage Difference Series โ Fewer wires โ Less likely to overheat โ All bulbs can be controlled with one switch โ If one bulb fails,all bulbs turn off โ Current is same everywhere โ Voltage shared Parallel โ Voltage is same everywhere โ Current is shared Explain how the voltage across the fixed resistor changes when temperature decreases (3) โ Increased resistance โ Less current โ Voltage decreases Why are the following things dangerous when using mains electricity at home
**- Fraying Cables- potential electrocution risk
- Long Cables- tripping hazard
- Water (and metal objects)- conduct electricity and could electrocute you Ways to prevent dangers of electricity:** โ Use double insulation โ Circuit breaker โ Fuse โ Earth wire How does a fuse protect? โ If the current becomes higher than the fuse rating โ The fuse melts โ Breaking the circuit
Advantage of circuit breakers over fuse โ faster and easier to reset Why is double insulation used โ Both wires inside a device and the outer case of device are insulated โ No chance of electrocution Why is heater fitted with earth wire โ metal casing โ metal conducts electricity Describe how earth wire acts as a safety feature (4) โ earth wire connected to metal casing โ if casing becomes live, earth wire provides low resistance path to earth โ fuse- when increased current, it melts โ which cuts of supply Series circuits have the same current throughout but the voltage is shared among the components Parallel circuits have same voltage but varying current VOLTMETER IS ALWAYS IN PARALLEL WHEN DRAWING A CIRCUIT Explain why LED flashes on and off in this circuit (2) โ alternating current switches direction โ LED only allows current to flow in one direction โ LED will not light up when current is flowing in opposite direction Type of wire Color Live brown Neutral blue Earth yellow/green Type of safety feature Role Fuse โ Excessive current โ Melts the fuse wire โ Breaks the circuit Earthing Circuit breaker
Longitudinal waves have vibrations that are parallel to the direction of energy movement All electromagnetic waves travel at the same speed in a vacuum. All waves transfer energy and information without transferring matter Type of wave Difference Example Transverse Consists of peaks and troughs all electromagnetic waves (eg. Radio waves) Water Waves Longitudinal has rarefactions and compressions Sound Waves P-waves State the name of the wave behavior responsible for the path of the ray of light as it passes from air into optical fiber (1) โ Refraction Explain the path of the ray of light as it travels through the optical fibre (3) โ enters the core of fibre โ core has higher refractive index than the cladding which causes light ray to be reflected back into the core it it attempts to escape โ As light ray travels through core, undergoes multiple reflections off the walls of the core due to the total internal reflection What are the two factors for total internal reflection? โ Angle of incidence greater than critical angle โ More dense to less medium What is meant by the term critical angle? โ the angle of incidence is beyond which total internal reflection occurs Explain the path of the ray of light as it travels through the optical fibre? โ (total internal) reflection; โ (because) core has higher refractive index than air; โ (because) angle (of incidence) is greater than critical angle; NO MOTION = NO WAVELENGTH = NO DOPPLER EFFECT Waves transfer energy and information without transferring matter
NOTE- if light does not change direction when it enters a new medium,this is because the ANGLE OF INCIDENCE is 0,so the ANGLE OF REFRACTION must also be 0 Explain why the wavelength of the light reduces when it enters the atmosphere. (2) โ Speed of wave decreases โ Speed = frequency x wavelength โ Frequency stays constant Suggest why the Sun appears not to be circular when it is close to the horizon at sunset. (1) โ Rays of light from different parts of the sun refract by different amounts Explain how the Doppler effect causes a change in the observed frequency of the waves (3) โ Speed of wave is constant โ If wave source is moving away,wavefronts spread out and wavelength increases โ Speed = frequency x wavelength โ Higher wavelength,constant speed= less frequency Pneumonic Type of wave Use Danger Ronaldo Radio communications No danger Mate Microwave Heat food Internal heating of body tissue Is Infrared night vision goggles Skin burn Very Visible light photography Endoscope Optical fiber cables Can cause blindness Under Ultraviolet fluorescent lamps Security (forgery) Ionising so it causes cancer (Wear sunscreen to prevent) X X-ray See bones Can damage healthy cells G Gamma sterilize medical equipment + food Can cause cancer Name part of electromagnetic spectrum that has lower frequency than microwaves โ radio waves
Energy resources and energy
transfers
Explain why the plastic cover reduces how much the water cools down at night. (4) โ Plastic cover traps air โ Air is a good insulator โ Plastic is a good insulator โ Conduction reduced โ Convection reduced โ Less evaporation Explain the energy transfers and stores when an object drops to the ground โ Before object dropped,has gravitational potential energy store โ As it is dropped,energy transferred mechanically โ Before it hits the floor,energy is transferred to kinetic energy store โ As it hits the floor,thermal energy store of surroundings increases โ Energy transferred to surroundings mechanically and by radiation (sound) How does a plastic cup with a vacuum and a shiny surface prevent heat loss: โ Plastic poor conductor โ Vacuum contains no particles โ Prevents conduction โ Plastic traps air โ Air good insulator,prevents convection โ Outer shiny surface poor emitter of radiation โ Energy transfer by radiation stopped Explain why temperatures of the hot water and cold water change โ Hot water loses thermal energy โ Hot water has higher temp than cold water, energy flows from hotter object to cooler objects โ Thermal energy transferred from hot water to cold water โ Energy transfer occurs through conduction Explain how placing a lid on the plastic cup would affect the results โ Energy transferred through convection and radiation would be reduced โ Leading to higher thermal equilibrium โ Time taken to cool to room temperature would be longer
Example sankey diagram: Explain how a convection current is formed in the air near the bar. โ Temperature of air increases โ Air expands โ Density of air decreases โ Warm air rises โ Cool air replaces warm air โ Process repeats
โ Particles collide with sides of walls of chamber โ Exert a force on wall โ force/area gives pressure
Magnetism and
electromagnetism
Describe a method he could use to determine the shape and direction of the magnetic field produced by a bar magnet. (3) โ Place magnet under card and sprinkle iron filings on card โ Tap card to reveal pattern โ Use plotting compass to show direction from north to south Explain how the magnetic field of bar magnet shows that the strength of the magnetic field changes (2) โ Field lines closest near poles โ Magnetic field stronger closer to magnet Explain what happens when there is a current in a coil (3) โ Coil produces magnetic field โ Interacts with magnetic field of bar magnet โ Produces a force acting on the coil โ Opposite forces on either side of the coil โ Coil rotates Give a reason why voltage is induced between the ends of the metal wire as it moved between the poles of the bar magnets (1) โ Magnetic Field lines are cut by the wire State two changes that could be made to this arrangement that would increase the magnitude of the induced voltage (2) โ The wire could be moved faster (with more frequency) โ A more powerful magnet could he used
Define magnetically hard: โ Difficult to magnetise โ Difficult to demagnetise Describe how two magnets can be arranged to produce a uniform magnetic field `(2) โ Two magnets with opposite poles facing โ Bring poles closer together Draw magnetism of a S-S pole:
Uniform magnetic field: โ Parallel lines โ Evenly spaced out Explain how a bicycle dynamo causes lights to turn on when bicycle moves โ Core gains magnetic field โ Changing magnetic field โ Field lines cut โ Voltage induced โ Causes current Explain how a generator works and produces voltage โ Turning handle makes coil rotate โ Coil cuts through magnetic field of permanent magnet โ Current induced Increase voltage: โ Turn coils faster โ Increase no. of turns on coil โ Use stronger magnet Explain how a loudspeaker works (motor effect) โ Loudspeaker has alternating current โ Changing magnetic field interacts with magnetic field of permanent magnet โ Causes a force to be exerted on speaker โ Alternating current causes force to change direction โ Causes speaker cone to vibrate Increase force on loudspeaker coil: โ Use larger current โ Increase strength of magnet โ Increase no. of turns on loudspeaker coil
โ Fission releases neutrons โ Neutrons captured by other uranium nuclei โ These nuclei undergo fission Note:A way to stop a chain reaction is by using control rods that are made of boron. The process of energy release in the core of a star is different to the process of energy release in a nuclear reactor in a power station. Describe how these processes of energy release are different (4) โ Stars use fusion,reactor uses fission โ Fusion is joining of nuclei โ Fusion involves light nuclei e.g. hydrogen โ Fission is the splitting of nuclei โ Involves heavy nuclei e.g. uranium Describe an experiment that a scientist could use to demonstrate that the emission from technetium-99 is gamma radiation. (5) โ Use geiger muller tube โ Measure background radiation count rate (by removing the radioactive source) โ Measure count rate with source โ Subtract to find count rate โ Repeat to find mean โ paper/aluminium does not affect count rate โ Lead will affect count rate significantly โ Keep distance from source โ Limit exposure time โ Use shielding: keep source in lead lined box,wear lead apron/gloves โ Handle radioactive source with tongs Nuclear reactor part Function Material Control rod Absorbs neutrons boron Moderator Slows down neutrons graphite Shielding Prevents irradiation lead/concrete/steel Fuel rod Provides fuell for fission uranium-235/plutonium Type of radiation Range Stopped by property Ionising
Alpha Few cm paper helium nucleus High Beta Few 10s cm Few mm aluminium 1 electron medium Gamma infinite Few mm lead electromagnetic wave Low Discuss precautions that must be taken when disposing of this radioactive waste. ( โ Use strong containers โ Use containers that cannot rust โ Rust-proof containers may be expensive to manufacture โ Dispose waste in site with low risk of earthquake โ Water table should not be high Safety precautions to reduce exposure to radiation: โ Handle source with tongs โ Store source in lead box when not in use โ Minimise time handling source,maximise distance from source โ Use shielding: lead apron
Astrophysics
Describe what happens to these high-mass stars when they leave the main sequence stage of their evolution. (3) โ Red supergiant โ Supernova โ Black hole/neutron star Pneumonic Star color Classification Bro Blue hottest When White
