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AQA GCSE Physics - Paper 2
The momentum of one thing is always equal to the momentum of another thing e.g. a skateboarder has the same momentum as the skateboard" "Equation for Momentum - CORRECT ANSWER Momentum (kg m/s) = mass (kg) x velocity (m/s) p=mv" "What is the conservation of momentum? - CORRECT ANSWER In a closed system, the total momentum before an event is the same as after the event" "What is a closed system? - CORRECT ANSWER When no external forces act" "Equation for Force 2 - CORRECT ANSWER Force (N) = Mass (kg) x Acceleration (m/s²) F=ma" "Equation for Force 3 - CORRECT ANSWER Force (N) = Change in momentum (kg m/s) / Change in time (s) F=mΔv/Δt" What are vectors? - CORRECT ANSWER Quantities that have a magnitude and a direction" "What are scalars? - CORRECT ANSWER Quantities that only have a magnitude" "Examples of vectors - CORRECT ANSWER Force Velocity Displacement Acceleration Momentum" "Examples of scalars - CORRECT ANSWER Speed Distance Mass Temperature Time" "What are contact forces? - CORRECT ANSWER Forces that act when two objects are touching" "What are non-contact forces? - CORRECT ANSWER Forces that act without the need for two objects to be touching"
"Examples of contact forces - CORRECT ANSWER Friction Air resistance Tension in ropes Normal contact force" "Examples of non-contact forces - CORRECT ANSWER Magnetic force Gravitational force Electrostatic force" "What is mass? - CORRECT ANSWER The amount of material an object is made of It is the same value everywhere Measured using a mass balance" "What is weight? - CORRECT ANSWER The force acting on an object due to gravity It depends on the strength of the gravitational field at the location of the object Measured using a calibrated spring balance - newtonmeter" "Equation for Weight - CORRECT ANSWER Weight (N) = Mass (kg) x Gravitational Field Strength (N/kg) W=mg" "What is weight directly proportional to? - CORRECT ANSWER Mass" "What are free body diagrams? - CORRECT ANSWER Diagrams that show all the forces acting on an object" "What is the minimum number of forces acting on an object in real situations? - CORRECT ANSWER At least 2 forces" "What is the resultant force? - CORRECT ANSWER The single force that replaces multiple forces acting at a single point" "How is work done? - CORRECT ANSWER When a force moves an object through a distance, energy is transferred and work is done on the object" "Equation for 'Work Done' - CORRECT ANSWER Work done (J) = Force (N) x Distance (m) W=Fs" "What is 1J equal to? - CORRECT ANSWER 1Nm" "What could happen when you apply a force to an object? - CORRECT ANSWER It may stretch, compress or bend"
"Longitudinal waves - CORRECT ANSWER The oscillations are parallel to the direction of energy transfer Examples are:
- Sound waves in air, ultrasound
- Shock waves e.g. some seismic waves" "What is the wave speed? - CORRECT ANSWER The speed at which energy is being transferred or the speed at which the wave is moving at" "Equation for Wave Speed - CORRECT ANSWER Wave Speed (m/s) = Frequency (Hz) x Wavelength (m) v=fλ" "What is the speed of sound in air? - CORRECT ANSWER 330m/s" "What does an oscilloscope do? - CORRECT ANSWER Along with two microphones, it is used to find the wavelength of sound waves" "What happens when waves arrive at a boundary between two different materials? - CORRECT ANSWER 1) The waves are absorbed by the material the wave is trying to cross into - transfers energy to the material's energy stores
- The waves are transmitted - they carry on travelling through the new material (often leads to refraction)
- The waves are reflected" "Rule for all reflected waves - CORRECT ANSWER Angle of incidence = angle of reflection" "What is the angle of incidence? - CORRECT ANSWER The angle between the incoming wave and the normal" "What is the angle of reflection? - CORRECT ANSWER The angle between the refracted wave and the normal" "What is the normal? - CORRECT ANSWER An imaginary line that's perpendicular to the surface at the point of incidence" "What is a specular reflection? - CORRECT ANSWER This happens when a wave is reflected in a single direction by a smooth surface E.g. when light is reflected by a mirror, you get a nice, clear reflection" "What is a diffuse reflection? - CORRECT ANSWER When a wave is reflected by a rough surface & the reflected rays are scattered in lots of different directions - happens due to the normal being different for each incoming ray, therefore the angle of incidence is different for each ray"
"Length of a radio wave - CORRECT ANSWER 1m-10⁴m" "Length of a microwave - CORRECT ANSWER 10⁻²m" "Length of a infrared wave - CORRECT ANSWER 10⁻⁵m" "Length of a visible light wave - CORRECT ANSWER 10⁻⁷m" "Length of an ultraviolet wave - CORRECT ANSWER 10⁻⁸m" "Length of an x-ray - CORRECT ANSWER 10⁻¹ m"⁰ "Length of a gamma ray - CORRECT ANSWER 10⁻¹⁵m" "EM continuous spectrum - CORRECT ANSWER 1) Radio waves
- Microwaves
- Infrared waves
- Visible light rays
- Ultraviolet waves
- X-rays
- Gamma rays" "What is refraction? - CORRECT ANSWER When a wave crosses a boundary between materials at an angle, it will change direction" "What affects the rate of refraction? - CORRECT ANSWER How much the wave speeds up/slows down - this depends on the density of the two materials If the wave slows down, it will bend towards the normal If the wave speeds up, it will bend away from the normal" "What happens during reFraction? - CORRECT ANSWER The wavelength of a wave changes but the frequency stays the same" "What is optical density? - CORRECT ANSWER A measure of how quickly light can travel through a material - the higher the optical density, the slower light waves travel through it" "What are EM waves made up of? - CORRECT ANSWER Oscillating electric and magnetic fields" "How are EM waves produced? - CORRECT ANSWER Alternating currents are made up of oscillating charges - as the charges oscillate, they produce oscillating electric & magnetic fields i.e. EM waves"
"Equation for Speed - CORRECT ANSWER Distance Travelled (m) = Speed (m/s) x Time (s) s=vt" "What is the typical speed of a person walking? - CORRECT ANSWER 1.5m/s" "What is the typical speed of a person running? - CORRECT ANSWER 3m/s" "What is the typical speed of a person cycling? - CORRECT ANSWER 6m/s" "What is the typical speed of a car? - CORRECT ANSWER 25m/s" "What is the typical speed of a train? - CORRECT ANSWER 55m/s" "What is the typical speed of a plane? - CORRECT ANSWER 250m/s" "What factors affect speed? - CORRECT ANSWER Fitness of the person Age of the person Distance travelled Terrain Climate Gender of the person" "What factors affect wind speed? - CORRECT ANSWER Temperature Atmospheric pressure Any large buildings or structures nearby e.g. forests reduce wind speed travelling through them" "What is acceleration? - CORRECT ANSWER The change in velocity in a certain amount of time" "Equation for Acceleration - CORRECT ANSWER Acceleration (m/s²) = Change in Velocity (m/s) / Time (s) a=Δv/t" "What is deceleration? - CORRECT ANSWER Negative acceleration - when something slows down, the change in velocity is negative" "What is constant acceleration? - CORRECT ANSWER Uniform acceleration - acceleration due to gravity is uniform for objects in free fall 9.8m/s² near the Earth's surface" "Equation for Uniform Acceleration - CORRECT ANSWER Final velocity² (m/s) - Initial velocity² (m/s) = 2 x Acceleration (m/s²) x Distance (m) v²-u²=2as"
"Distance-Time Graphs - Features - CORRECT ANSWER 1) Gradient = speed
- Flat sections = object is stationary
- Straight uphill sections = object is travelling at a steady speed
- Curves = object is accelerating or decelerating
- Steepening curve = object is speeding up
- Levelling off curve = object is slowing down" "Velocity-Time Graphs - Features - CORRECT ANSWER 1) Gradient = acceleration
- Flat sections = object is travelling at a steady speed
- Uphill sections = object is accelerating
- Downhill sections = object is decelerating
- Curves = object is changing acceleration The steeper the graph, the greater the acceleration or deceleration" "What does friction do? - CORRECT ANSWER It causes objects to slow down when they rub against another surface It always acts in the opposite direction to movement It's always smaller than the driving force" "Where do you get friction? - CORRECT ANSWER When two surfaces are in contact or when an object passes through a fluid (drag)" "What is drag? - CORRECT ANSWER The resistance you get in a fluid Air resistance is a type of drag" "How do you reduce drag? - CORRECT ANSWER Keep the shape of an object streamlined" "Process of a falling object - CORRECT ANSWER 1) When a falling object first sets off, the force of gravity is much more than the frictional force slowing it down, therefore the object accelerates
- As the speed increases, the friction builds up
- The acceleration is gradually reduced until eventually, the friction force is equal to the accelerating force - the resultant force is 0
- At this point, it will have reached maximum speed or terminal velocity and will fall at a steady speed" "What does air resistance do? - CORRECT ANSWER It causes things to fall at different speeds" "What determines the terminal velocity? - CORRECT ANSWER The terminal velocity of any object is determined by its drag in comparison to its weight" "What affects the frictional force? - CORRECT ANSWER The shape and area of an object"
"What is thinking distance affected by? - CORRECT ANSWER 1) Speed - the faster you're going, the further you'll travel during your reaction time
- Your reaction time - the longer it is, the longer your thinking distance
- Alcohol
- Drugs
- Sleep deprivation
- Distractions" "What is braking distance affected by? - CORRECT ANSWER 1) Speed - the faster a vehicle travels, the longer it takes to stop
- Weather/Road surface - if it's wet or icy, there is less grip (and less friction) between a vehicle's tyres and the road, which can cause tyres to skid
- Condition of tyres - if the tyres are bald, then they cannot get rid of water in wet conditions, thus leading to skidding on top of the water
- Quality of brakes - if brakes are worn or faulty, they won't be able to apply as much force as well-maintained brakes, which could be dangerous when wanting to brake hard" "What happens when the brake pedal is pushed? - CORRECT ANSWER The brake pads are pressed onto the wheels, thus causing friction, which causes work to be done. The work done between the brakes and the wheels transfers energy from the kinetic energy stores of the wheels to the thermal energy stores of the brakes, which as a result, increase in temperature" "What happens when a vehicle is going really fast? - CORRECT ANSWER It has more energy in its kinetic energy stores, so the more work needs to be done to stop it - a greater braking force will be needed to make the vehicle stop within a certain distance, therefore the deceleration will be larger The larger the deceleration, the more dangerous it will be as the brakes could overheat or cause the vehicle to skid" "What is the typical reaction time? - CORRECT ANSWER Between 0.2s and 0.9s" "Typical thinking distances - CORRECT ANSWER 30mph - 9m 50mph - 15m 70mph - 21m" "Typical space needed to be left for stopping distances - CORRECT ANSWER 30mph - 6 car lengths 50mph - 13 car lengths 70mph - 24 car lengths" "What is momentum? - CORRECT ANSWER How much 'oomph' an object has All moving objects have it
"What happens when an object is inelastically deformed? - CORRECT ANSWER The object won't return to its original shape and length after the force has been removed" "Equation for Force 1 - CORRECT ANSWER Force (N) = Spring Constant (N/m) x Extension (m) F=ke" "What is extension directly proportional to? - CORRECT ANSWER The force applied F∝e" "The stiffer the spring... - CORRECT ANSWER ...The greater the spring constant" "What is the limit of proportionality? - CORRECT ANSWER The point at which extension is no longer directly proportional to force" "Equation for 'Moments' - CORRECT ANSWER Moment of a force (Nm) = Force (N) x Distance (m) M=Fd" "What is a moment? - CORRECT ANSWER The turning effect of a force" "When will an object not turn? - CORRECT ANSWER When the object is balanced - the total anticlockwise moment equals the total clockwise moment about a pivot" "What affects the size of a moment? - CORRECT ANSWER 1) The size of the force applied - a larger force will produce a larger moment
- The perpendicular distance from the pivot to the line of action of the force - any angle smaller than 90° will result in a smaller distance, thus a smaller moment" "What do levers do? - CORRECT ANSWER They increase the distance from the pivot at which the force is applied" "Do levers make it easier or harder to do work? - CORRECT ANSWER Easier to do work" "What are gears and what do they do? - CORRECT ANSWER Circular discs with 'teeth' around their edges Their teeth interlock so that turning one causes another to turn in the opposite direction They are used to transmit the rotational effect of a force from one place to another" "What is pressure? - CORRECT ANSWER The force per unit area" "Equation for Pressure - Surface of a fluid - CORRECT ANSWER Pressure (Pa) = Force normal to a surface (N) / Area of that surface (m²) p=F/A"
"Investigating Motion - Method - CORRECT ANSWER 1) Set up the apparatus. Set up the trolley so it holds a piece of card with a gap in the middle that will interrupt the signal on the light gate twice. If you measure the length of each bit of card that will pass through the light gate & input this into the software, the light gate can measure the velocity for each bit of card - can use this to work out the trolley's acceleration
- Connect the trolley to a piece of string that goes over a pulley & is connected on the other side to a hook
- The weight of the hook & any masses attached to it will provide the accelerating force, equal to the mass if the hook x acceleration due to gravity
- The weight of the hook & masses accelerates both the trolley & the masses, so you're investigating the acceleration of the system
- Mark a starting line on the table the trolley is on so that the trolley always travels the same distance to the light gate
- Place the trolley on the starting line, holding the hook so the string is taut, and release it
- Record the acceleration measured by the light gate as the trolley passes through it - acceleration of the whole system
- Repeat twice more to get an average" "Investigating the Effect of Mass on Acceleration - CORRECT ANSWER Add masses to the trolley one at a time to increase the mass of the system. Don't add masses to the hook, or you'll change the force. Record the average acceleration for each mass" "Investigating the Effect of Force on Acceleration - CORRECT ANSWER Keep the total mass of the system the same, but change the mass on the hook. Start with all the masses loaded onto the trolley, and transfer the masses to the hook one at a time, to increase the accelerating force. The mass of the system stays the same as you're only transferring the masses from one part of the system to another. Record the average" "Why do you weigh more on a bigger planet? - CORRECT ANSWER There is a stronger gravitational pull towards the planet's centre" "What is hydraulic pressure? - CORRECT ANSWER The pressure that is caused by a liquid Pressure in a liquid is caused by the weight of the air above it" "Pressure in a liquid - CORRECT ANSWER 1) Acts in all directions
- Increases with depth" "What is terminal velocity? - CORRECT ANSWER The constant speed that a freely falling object eventually reaches when the air resistance prevents further acceleration" "What effects does gravity produce when it attracts all masses? - CORRECT ANSWER
- On the surface of a planet, it makes all things fall towards the ground
- It gives everything a weight"
"What happens when an object has been elastically deformed? - CORRECT ANSWER It can return to its original shape and length after the force has been removed All energy is transferred to the object's elastic potential energy store" "How are radio waves produced? - CORRECT ANSWER They are produced using an alternating current in an electrical circuit When transmitted radio waves reach a receiver, the radio waves are absorbed. The energy carried by the waves is transferred to the electrons in the material of the receiver. This energy causes the electrons to oscillate & if the receiver is part of a complete electrical circuit, it generates an alternating current - this current will have the same frequency as the radio waves that generated it" "Radio Waves - CORRECT ANSWER EM radiation with wavelengths longer than 10cm Long-wave radio signals can be transmitted long distances - they diffract around the curved surface of the Earth, thus they can be received even if the receiver isn't in the line of sight of the transmitter Short-wave radio signals (10m-100m) can be received at long distances - they are reflected from the ionosphere Medium-wave signals can also reflect from the ionosphere, depending on atmospheric conditions & the time of day" "Everyday Radio Waves - CORRECT ANSWER 1) Bluetooth uses short-wave radio signals to send data over short distances between devices without wires
- Waves used for TV & FM radio transmissions have very short wavelengths - to get reception, you must be in direct sight of the transmitter" "Microwaves - Satellite Communication - CORRECT ANSWER Used for communication to and from satellites Slight time delay between a signal being sent & received from a satellite due to the long distance it's had to travel" "Satellite TVs - CORRECT ANSWER The signal from a transmitter is transmitted into space where it's picked up by the satellite receiver dish orbiting above the Earth - the satellite then transmits the signal back to Earth in a different direction where it's received by a satellite dish on the ground" "Microwaves - Microwave Ovens - CORRECT ANSWER The microwaves need to be absorbed by the water molecules in food - use a different wavelength to those used in satellite communication The microwaves penetrate up to a few centimetres into the food before being absorbed and transferring the energy they are carrying to the water molecules - causes the water to heat up The water molecules then transfer this energy to the rest of the food molecules by heating - quickly cooks the food"
"Low Frequency Waves - CORRECT ANSWER Don't transfer much energy and mostly pass through soft tissue without being absorbed" "High Frequency Waves - CORRECT ANSWER Transfer lots of energy & so can cause lots of damage, e.g:
- UV radiation damages surface cells, which can lead to sunburn & cause skin to age prematurely - some more serious effects include blindness & an increased risk of skin cancer
- Gamma rays & x-rays are types of ionising radiation - can cause gene mutation or cell destruction & cancer" "What is radiation dose? - CORRECT ANSWER A measure of the risk of harm from the body being exposed to radiation The risk depends on the total amount of radiation absorbed & how harmful the type of radiation is Measured in sieverts (Sv) or millisieverts (mSv)" "CT scans - CORRECT ANSWER Uses X-rays & a computer to build up a picture of the inside of a patient's body Head = 2.0mSv Chest = 8.0mSv A CT scan on someone's chest means they are four times more likely to suffer damage to their genes than if they had a head scan" "Convex Lens - CORRECT ANSWER Bulges outwards & causes rays of light parallel to the axis to be brought together (converge) at the principal focus - where the rays hitting the lens parallel to the axis all meet" "Concave Lens - CORRECT ANSWER Caves inwards & causes parallel rays of light to spread out (diverge) The principal focus is the point where rays hitting the lens parallel to the axis appear to all come from - they meet up at a point behind the lens" "What is the focal length? - CORRECT ANSWER The distance from the centre of the lens to the principal focus" "Rules for Refraction - Convex Lens - CORRECT ANSWER 1) An incident ray parallel to the axis refracts through the lens & passes through the principal focus on the other side
- An incident ray passing through the principal focus refracts through the lens & travels parallel to the axis
- An incident ray passing through the centre of the lens carries on in the same direction"
"Rules for Refraction - ConcavE Lens - CORRECT ANSWER 1) An incident ray parallel to the axis refracts through the lens & travels in line with the principal focus (it appears to have come from the principal focus)
- An incident ray passing through the lens towards the principal focus refracts through the lens & travels parallel to the axis
- An incident ray passing through the centre of the lens carries on in the same direction" "What is a real image? - CORRECT ANSWER Where the light from an object comes together to form an image on a 'screen' - like the image formed on the eye's retina" "What is a virtual image? - CORRECT ANSWER When the rays are diverging, so the light from the object appears to be coming from a completely different place" "How do you describe an image? - CORRECT ANSWER 1) How big it is compared to the object
- Whether it's upright or inverted relative to the object
- Whether it's real or virtual" "What type of image do concave lenses always produce? - CORRECT ANSWER A virtual image - the image is the right way up, smaller than the object & on the same side of the lens as the object" "Magnifying Glasses - CORRECT ANSWER Use a convex lens The object being magnified must be closer to the lens than the focal length A magnified virtual image is created - the light rays don't actually come from the place where the image appears to be" "Magnification Formula - CORRECT ANSWER Image height = Magnification x Object Height" "What part of the EM spectrum do we see? - CORRECT ANSWER Visible light - a range of wavelengths we perceive as different colours" "Wavelength of violet - CORRECT ANSWER 400nm" "Wavelength of red - CORRECT ANSWER 700nm" "What colours can't you make by mixing? - CORRECT ANSWER Pure red, green and blue" "What happens when all the different colours are put together? - CORRECT ANSWER White light is created" "Opaque objects - CORRECT ANSWER Don't transmit light When visible light hits them, they absorb some wavelengths of light & reflect others
It will increase more rapidly for shorter wavelengths" "What do all objects emit? - CORRECT ANSWER Electromagnetic radiation - due to the energy in their thermal energy stores" "What does the overall temperature of the Earth depend upon? - CORRECT ANSWER The amount of radiation it reflects, absorbs and emits" "Will more radiation be absorbed when it's day or night? - CORRECT ANSWER Day - the Sun transfers radiation to the Earth where it is absorbed, thus causing an increase in local temperature" "Global warming - CORRECT ANSWER If the atmosphere starts to absorb more radiation without emitting the same amount, the overall temperature will rise until absorption and emission are equal again" "What causes sound waves? - CORRECT ANSWER Vibrating objects - these vibrations are passed through the surrounding medium as a series of compressions and rarefactions" "Travelling of Sound Waves - CORRECT ANSWER Sound waves travel faster in solids than in liquids, and faster in liquids than in gases When a sound wave travels through a solid, it does so by causing the particles in the solid to vibrate" "Where can't sound travel? - CORRECT ANSWER Space - it's mostly a vacuum, therefore there are no particles to move or vibrate" "Process of sound reaching the ear - CORRECT ANSWER 1) Sound waves that reach your eardrum can cause it to vibrate
- These vibrations are passed on to tiny bones in your ear called ossicles, through the semicircular canals & to the cochlea
- The cochlea turns these vibrations into electrical signals which get sent to your brain & allow you to sense the sound" "What range frequency can humans hear? - CORRECT ANSWER Between 20Hz and 20kHz" "What limits human hearing? - CORRECT ANSWER 1) The size of our eardrum
- The shape of our eardrum
- The structure of all the parts in the ear that vibrate to transfer the energy from the sound wave" "Sound Waves - Reflection - CORRECT ANSWER Sound waves are reflected by hard, flat surfaces Echoes are just reflected sound waves"
"Sound Waves - Refraction - CORRECT ANSWER Sound waves will refract as they enter different media As they enter denser material, they speed up - when a wave travels into a different medium, its wavelength changes and its frequency stays the same, thus causing the change in speed" "The stronger the magnetic field... - CORRECT ANSWER ...The closer together the magnetic field lines are" "Where is the magnetic field strongest? - CORRECT ANSWER At the poles of the magnet - the magnetic forces are always strongest at the poles" "Two of the same poles = - CORRECT ANSWER Repulsion of each other" "Two different poles = - CORRECT ANSWER Attraction to each other" "What do compasses do? - CORRECT ANSWER They show the direction of magnetic fields - they contain a tiny bar magnet whose north pole is attracted to the south pole of any other magnet it is near" "Why do compasses always point north? - CORRECT ANSWER The Earth generates its own magnetic field - magnetosphere Shows the core of the Earth must be magnetic The core is solid iron surrounded by molten iron - movement of molten iron around the core creates the field" "What are the two types of magnet? - CORRECT ANSWER Permanent magnet & induced magnet" "Permanent magnets - CORRECT ANSWER They produce their own magnetic field They are attracted to induced magnets" "Induced magnets - CORRECT ANSWER They are magnetic materials that turn into a magnet when they're put into a magnetic field They're attracted to permanent magnets When you take away the magnetic field, they quickly lose their magnetism and stop producing a magnetic field" "What happens when a current flows through a wire? - CORRECT ANSWER A magnetic field is created around the wire - the field is made up of concentric circles perpendicular to the wire, with the wire in the centre Changing the direction of the current changes the direction of the magnetic field" "The larger the electric current... - CORRECT ANSWER ...The stronger the magnetic field will be"
