The whole of AQA Physics Paper 2 in only 47 minutes!! GCSE 9-1 Revision

– Hey, guys, here is a summary video of everything you need for your second physics exam for AQA Now this is a really, really long video There is so much stuff you need to learn in here, loads and loads of equations, loads and loads of units You have to learn these if you want to do well To help you, I’ve written a ridiculously long revision guide which you can get for free from my website, or you can go and get it from Amazon (gentle music) A scalar quantity is going to be just a number A vector quantity is going to be a number and a direction For example, distance is scalar, but displacement is vector, because it’s distance in a direction Mass is scalar, but weight, which is your mass upon the Earth, is vector Speed is scalar, but velocity, which is speed in a certain direction, is vector Acceleration and force are both vector And momentum is also vector If we’re looking for the resultant force, we need to find the difference between them For example, here we have 10 plus 10 newtons minus five newtons is going to give us plus five newtons, which is going to be five newtons in that direction For the second one, we have plus two newtons minus plus two newtons, giving us zero newtons as the overall resultant force So there is going to be no movement Your weight is not the same as your mass, because your weight is equal to your mass times gravity Your weight is measured in newtons Your mass is measured in kilograms And gravity is measured in newtons per kilogram So your mass swill never change, but your weight will change depending on the planet or depending on gravity, which is why when they went to the moon, they were basically weightless, so they could jump around Another W here, work equals force times distance Work is measured in joules Force is measured in newtons And distance is measured in meters So that one joule is equal to one newton-meter When you exert a force on an object, it is going to be squashed or stretched or deformed in some way Here, I’ve done an experiment for you This is commonly known as Hooke’s Law What I’ve done is taken a spring This is the bottom of the spring, kept marked in every single photo, and I’ve added weights on to the bottom of it You can see that the length of the spring is getting longer the more weights are added on to the bottom of it We can plot what happens in Hooke’s Law, because it is a direct line until we get to a certain point, and this point is the limit of proportionality Before that, it is going to stretch So the more force we add on, as we increase force, the extension’s going to be increased After we get to the limit of proportionality, no matter how much force you add on, it is not going to stretch anymore It is potentially going to snap Force equals the spring constant times extension Force is measured in newtons Extension is measured in meters And the spring constant is measured in newtons per meter Kinetic energy is equal to 1/2 times mass times velocity-squared Kinetic energy is measured in joules Mass is measured in kilograms Velocity is measured in meters per second And with this, the squared is just around the meters per second So you have to that bit first A fluid can either be a liquid or a gas Liquids are incompressible, and the exam boards like that word,

whereas gases are compressible Pressure equals force over area The units of pressure are pascals For force, it is newtons And for area it is meters-squared I have seen exam questions which use newtons per meter-squared for pressure If they do that in the exam question, give your answer in the same format I’ve also seen exam questions where they’ve done newtons per centimeter-squared So if the question is in that format, give your answer in that format This is one that you have to pay attention to, because they could be sneaky here Pressure, with a P, equals height times density, which is a lowercase rho, times gravitational field strength Pressure is measured in pascals Height is measured in meters Density is measured in kilograms per meters-cubed Gravitational field strength is 9.8 newtons per kilogram There is a lot of math in this topic And to give your brain a little break, here are some cute kittens for you to look at Distance equals speed times time Distance is measured in meters Speed or velocity is measured in meters per second Time is measured in seconds Distance-time graphs tell us lots of information If we have a slope that is increasing, we are moving And the steeper the slope, the faster we’re moving If it is a flat line, it is not moving We can see that as time is increasing, our distance is not increasing So in a distance-time graph, the flat bit is not moving We can calculate speed as the gradient Gradient is up over across, which is going to be distance over time Velocity-time graphs look very similar to distance-time graphs but are different For example, at our flat bit here, it is now moving, but it is going at a steady speed We can see that when they are increasing, they are accelerating So we now know that acceleration is equal to the gradients And that’s up over across or velocity over time If we want to work out the distance traveled, that’s the area under the graph For this section here, it is a triangle So to work that out it is going to be 1/2 times base times height For this section here, that is a rectangle So that is going to be base time height This section in the middle here is a bit more complicated, because we have a triangle, a rectangle and a triangle So that is base times height plus 1/2 times base times height And the height is the height of the triangle there Acceleration is equal to the change in velocity over time We can work out the change in velocity by taking the final velocity and minusing the initial velocity and the time taken by taking the final time and minusing the initial time Acceleration is in meters per second-squared Velocity is in meters per second And time is in seconds Final velocity-squared minus initial velocity-squared is equal to two times acceleration times distance Velocity, final and initial, is measured

in meters per second Acceleration is in meters per second-squared And distance is in meters When you are falling or when something is falling, terminal velocity is going to be reached when all forces are balanced A velocity-time graph of this would be very fast acceleration as the object initially started to fall As the object started to balance out, that would slow And when they reached terminal velocity, there would be no further increase in speed When you’re free-falling under gravity, your speed is going to be 9.8 meters per second, which is the same as the value of gravity, which is 9.8 newtons per kilogram Here we have a Newton’s cradle, which really elegantly demonstrates a number of physics principles First of all, inertia, an object that is in motion will remain in motion unless acted on by an outside force An object at rest will remain in rest unless acted on by an outside force So those balls in the middle are only going to move if something hits them And those balls on the outside are only gonna stop if something stops them It demonstrates the conservation of energy, where the balls only slow down as they lose energy to other things In this case, you won’t hear it, but it’s losing here energy to sound, and it’s losing energy to a bit of friction within the air This will keep going for as long as there is energy within the system And it also demonstrates Newton’s third law, where with every action, there is an equal and opposite reaction And we an see this as the balls keep hitting each other Inertia is when an object at rest will remain at rest unless acted upon by a force, and an object in motion will remain in motion, unless acted on by an outside force You can put this into action if you’re driving along, and you have your seat belt on The car brakes You would not brake as well, unless you are acted on by a force, that force being your seat belt Conservation of energy, energy is never created or destroyed It is only turned into something else Here, it is being turned into sound and a little bit of heat And for every action, there is an equal and opposite reaction Force equals mass times acceleration Force is measured in newtons Mass is measured in kilograms And acceleration is measured in meters per second-squared Stopping distance for a car is going to be made up of two things, thinking distance and braking distance And you can see that the faster you’re going, the more the stopping distance and the thinking distance increases This is because for thinking distance, your brain needs to firstly see the image The signal gets sent to your brain, is processed, and the signal gets sent all the way down to your foot And the faster you’re going, the more distance you’ll travel in the time that takes Things that affect thinking distance are going to be drinking alcohol It’s negatively going to affect it Taking illegal drugs is negatively going to affect it But taking something like caffeine is going to positively affect it Tiredness is going to negatively affect it Things that are going to affect braking distance are the conditions of the tires So nice, new tires are going to stop much quicker than old tires, which don’t have much grip on the road The condition of the road, so a snowy, icy road is going to have much longer braking distance than a new road or a road that has a lot of grit on it, is also going to have a long braking distance And the weight of a car, a heavy, heavy car is going to take much longer to stop There are a large number of features in a car designed to make it safer First of all, seat belts, baby seats, believe it or not, when I was brought home in the car, I was literally just put in the car, crumple zones in the front, air bags are a few of the examples We are about halfway through, so you get another tiny, little mind break Aren’t these guys so cute? Don’t they just inspire you to revise more? Momentum is mass times velocity Mass is measured in kilograms Velocity is measured in meters per second And the momentum is measured in kilogram, with a space, meters per second I know there’s a temptation to put another line in there, but that would be wrong

The law of conservation of momentum says that momentum is always conserved, which in calculations means your momentum before is going to equal your momentum afterwards So if you have two objects colliding, that momentum together before is equal to the colliding objects afterwards A transverse waves goes up and down From one point to another point, and this is my wave from the top to the bottom, the middle to the middle, we have the wavelength The amplitude is measured from the middle to the top or from the middle to the bottom The direction of movement for this is up and down This will also be the direction of oscillation And the direction of energy transfer is sideways Here we have our longitudinal wave where we have areas of compression and areas of refraction We can measure the wavelength in this, from one point to another point The direction of movement is side-to-side and so is the direction of energy Frequency is the number of waves per second So if we look at this block here as a second in time, some of them have a low frequency We’re not gonna see many peaks in one second But something that had a high frequency, we would see lots of peaks or lots of waves within one second You’ll notice that for the high frequency one, it has a low wavelength Whereas for the low frequency one, it has a high, or a long, wavelength If you want to measure the time period for something, that is one over the frequency Time is measured in seconds And frequency is measured in hertz There is a capital H and a lower case z Do not write lowercase, both letters, or uppercase, both letters, because they are wrong If you want to measure the speed of a wave, we can use a ripple tank This here will go in and out of the water, creating waves From this, we can measure a wavelength and also look at how many waves pass a certain point in a second, frequency Then we can use our equation to work out the speed of the wave V equals f times lambda To work out the speed of a wave, wave speed, we can take the frequency and times it by the wavelength Our units for speed are in meters per second Frequency is in hertz, capital H, lowercase z And wavelength is in meters Here we have the electromagnetic spectrum, from radio waves, microwaves, infrared, visible light, ultraviolet, X-ray and gamma rays Over here, these ones are high energy And these are low energy These are going to have a high frequency and these ones, a low frequency These are going to have a short wavelength and these, a long wavelength

Wavelength for radio waves can stretch into the meters, the kilometers, very, very long wavelengths Radio waves can be used for radio communications Microwaves can be used for mobile phones and for heating food Infrared are used for things like the light on your remote control You can also use it for heat sensing Visible light is used for cameras and your eye Ultraviolet can be used for detecting things like fake money X-rays are used for broken bones And gamma rays can be used for treating cancers or sterilizing things like killing bacteria Diffraction happens when a wave passes through a gap Here we have a small gap, and here we have a large gap And the wave will curve around as it comes out of that gap The amount of curvature, the amount of diffraction, will depend on the size of the gap Refraction happens when a wave passes from medium into another medium, say from air into glass or air into water And it will change direction So here is our normal here, move it down to here It will change direction as it goes through there And the reason it changes direction is because the wave changes speed But different parts of the wave change speed at different points So this part, down here, that hits first, is going to change speed, either getting faster or slower before this part of the wave, up here, which hasn’t changed medium or speed yet Lots of different surfaces will emit and absorb radiation Some will do it better than others Over on the right-hand side, you can see the practical and the required practicals that I’ve done for you Good absorbers are going to be dark surfaces and matt surfaces Good emitters are going to be dark, matt surfaces Good reflectors are going to be shiny surfaces When we have two like poles, we’re going to repel, but when we have two unlike polls, they’re going to attract A permanent magnet is going to have a magnetic field which goes from north to south And we can induce a magnet, a temporary magnet, if we place something inside that magnetic field Magnetic materials are going to be metals, and that is going to include iron, nickel and cobalt You can easily make an electromagnet at home All you need is a battery, some wire and an iron nail, because all an electromagnet is is an iron core with a wire around it connected up to a current You can use this to pick up things like paperclips or iron filings When a current is passed through the wire, it creates a magnetic field around the wire And this, in turn, strongly magnetizes the iron bar, thus creating our electromagnets If you want to change the strength of an electromagnet, you can do two things You can change the current Or you can change the number of turns, or the number of coils, that the wire, times the wire is wrapped around the iron core For Fleming’s left-hand rule, we need to make our left hand in this shape here, so your finger pointing up, thumb up, finger out And your first finger is your magnetic field This finger here is the current And then your thumb is the movement of the force And what you need to do when you have an exam question is literally you contort your hand until it fits in the right direction So the first one is nice and easy My field is going in that direction My current is going in that direction So the movement of the force is going upwards This one here is bit more complicated, ’cause this finger needs to be pointing in that direction My current needs to be going down

And then my thumb is going into the page We can change the size of the force by changing the current, by changing the strength of the magnet or by changing the angle between the wire and the magnetic field lines The greatest force is when the wire is perpendicular with magnetic field lines, and the force is going to be zero if the wire and the field lines are parallel Magnetic flux density is the amount of magnetic flux in a certain area, and the equation that we use for this is force equals magnetic flux density times current times length You’ll notice, really annoyingly, that this is an uppercase I and a lowercase l Our units for this, for force, are newtons For magnetic flux density, they are tesla For current, it is amps And for length, it is meters While this is called a simple electric motor, there’s actually quite a lot of physics going on in here And for this, we really need to use our Fleming’s left-hand rule So our magnetic field is going from north to south like this Our current is moving actually in two different directions On this side, it’s moving in this direction, and on the other side, it is moving in this direction So what we are going to have is that when the wire is moving past the south bit of the magnet, the force is going to be going down And when it’s moving past the north face of the magnet, the force is going to be going up And because one side is being pushed down, and the other side is being pushed up, it is going to turn around A moving coil loudspeaker works by making the diaphragm attached to a coil vibrate While we have a current passing through the coil, the force that is generated by the motor effect makes the coil move Every time the current changes direction, the force reverses direction So the coil is gonna be going back and forwards, making the diaphragm go back and forward, generating the sound waves A moving coil microphone works with the same principle but in the opposite direction Sound causes the diaphragm to vibrate The diaphragm is attached to the coil The vibration of the diaphragm moves the coil, which is gonna cause the coil to move backwards and forwards past the magnet Awesome work for making it to the end, guys I know this video is a slog to get through The rest of this is physics only If our forces are unbalanced, for example, if this force is bigger than this force, we’re going to have a turning effect, whether that be clockwise or anticlockwise If they are balanced, if this force and this force are the same, then we are not going to have a turning effect The moment equals force times distance Moment is measured in newton-meters Force is measured in newtons Distance is measured in meters Force is equal to mass times the change in velocity over the change in time Force is measured in newtons Mass is measured in kilograms Velocity is measured in meters per second And time is measured in seconds When a wave is reflected, it is going to come in, meet the boundary and then be reflected off Our angle of incidence is always going to be equal to our angle of reflection So we can always say that i equals r Your normal line is in the middle here It is a dash line, and it is drawn at 90 degrees to the mirror or the surface

that the wave is being reflected off If we have a sound wave instead of a light wave that is being reflected, we are going to get an echo A sound wave is a longitudinal wave It vibrates the air particles And your ear drum, in here, will pick up the vibration of the air particles and turn it into sound which your brain can interpret The range of human hearing is 20 hertz to 20 kilohertz We can use echo or ultrasound to determine distance And we can do that, because speed equals distance over time So if we know the speed of the wave, we can measure the time taken, and we can calculate the distance So a vessel exploring the sea can send down an ultrasound and measure the time it takes to come back And the time it takes to come back will be shorter or longer depending on the distance Now the really, really important thing to note here is that it is there and back again So the time is double what it would be, because the time it takes to get there and back is twice just the time it takes to get there So if you have an echo or an ultrasound calculation, you need to find distance You need to think logically about the time calculation that you’re using Ultrasounds can also be used for medical imaging Here is my massive bump Here was my massive baby And you can see the hard parts, the jaw, the skull, the legs, they are going to reflect the ultrasound much more than the liquid or the soft tissue parts When an earthquake occurs, we can use the resulting waves It gives information about the structure of the Earth P waves are primary waves They are longitudinal They can travel through solids and liquids, which means they can travel all the way through the Earth So if an earthquake happens over here, the P waves are gonna go all the way through, including through the solid core S waves are secondary waves They are transverse waves And they can only go through solids So they can’t go through liquids And because of these two different types of waves and how they’re detected on the opposite side of the Earth, this tells us information about the structure of the Earth A converging lens is shaped like this And this is the shorthand for it It is used to correct long-sightedness It’s going to produce a real image And it’s the type of lens used in magnifying glasses I have made many, many videos showing how to do ray diagrams, but just as a quick recap, for a converging lens, your first line needs to go from the top to the lens, and then on the other side, through the primary focus Your second line needs to go from the top through the middle I should extend that line a touch Your third line goes from the top through the focus until it gets to the axis Then it runs parallel with the axis, and it’s going to be there Then, over here, we are going to get our image formed And that image is going to be upside down So the top is there And the top is there Your diverging lens is going to be curved in like this, and this is the shorthand It’s going to correct short-sightedness It’s gonna give us a virtual image which is upright but smaller Drawing a diverging lens, our first line goes from the top

of the object to the axis And then we need to backtrack through the focus on the same side So I’m just gonna draw a dash line here And then the line will actually go like that And our second line needs to go from the top of the object through the middle And where those two points cross, there is going to be our virtual image Magnification is worked out by taking our image height and dividing it by the object’s height And you’ll be delighted to know that there are no units for this So I won’t be nagging you about this one Using a prism, or water in this circumstance, visible light can be broken up into its different parts, red, orange, yellow, green, blue, indigo, violet Red light is gonna have a wavelength of seven times 10 to the minus seven meters, moving through to violet, which is gonna have a wavelength of four times 10 to the minus seven meters Frequency, we’re looking at the other way around, so the frequency of red light is going to be four times 10 to the 14 hertz, whereas indigo is going to be seven times 10 to the 14 hertz Everything emits infrared radiation And this is the balance between the amount of energy, or the temperature, of the heat that is being absorbed and the amount that is being emitted at the same time This can tell us a lot about the temperature of an object by looking at the wavelength that are being emitted Now a black body is an object in space which is going to perfectly absorb radiation It does not emit it It absorbs it The generator effect is just an extension of Fleming’s left-hand rule When we have a wire and we move it through a magnetic field, we are going to be generating a current In a transformer, we have a soft iron core We have a wire, which is going to be coiling around And you’ll notice there are different number of coils here We are going to be looking at varying number of coils so that we can vary the voltage that goes into and comes out of our transformer If we have a step-up transformer, the secondary voltage is gonna be greater than the primary voltage So the voltage coming out is gonna be greater than the voltage going in If we have a step-down transformer, the secondary voltage is going to be less than the primary voltage So the voltage coming out is going to be less than the voltage going in When we are looking at transformers calculations, we have voltage in the primary coil divided by voltage in the secondary coil equals the number of turns in the primary coil divided by the number of turns in the secondary coil Our units for this are going to be for voltage That is volts And number of turns doesn’t have a unit, because it’s just a number You need to know that voltage in the secondary coil times the current in the secondary coil is equal to voltage in the primary coil times the current in the primary coil And our units for voltage are volts, for current, amps, voltage-volts, current-amps Our solar system is a beautiful, varied and fascinating thing Starting with the sun, all the way over here, we move through Mercury, Venus, Earth, Mars, and our moons, the asteroid belt, with some dwarf planets, and I’ll come back to these in a second, Jupiter, Saturn, Uranus, Neptune and poor Pluto down here, which isn’t a planet anymore It’s just a dwarf planet To help you remember the order, we have My Very Easy Method Just Speeds Up Naming, and then it used to be Planets, at the end, but Pluto isn’t a planet anymore So it’s now My Very Easy Method Just Speeds Up Naming

If you guys have any other ways that you remember the order of the planets or anything else, put that in the comments below, ’cause I’m sure loads of other people would love to see what you come up with So poor old Pluto, here, it used to be a planet It is now a dwarf planet I might do a separate video on why Pluto is now a dwarf planet But our dwarf planets are here, here, here and here I’m not gonna try and pronounce some of these names, ’cause I’m very, very sure I will get it wrong And we have an asteroid belt in between Mars and Jupiter and then another belt of large objects right on the edge The galaxy that we live in is the Milky Way And here, you can see the Milky Way stretching across the sky We are on the edge of the Milky Way On one of the arms right on the outside in the middle is a black hole Here we have the life cycle of a star It is going to start off as a cloud of dust and gas And these are going to come together under the force of gravity, because everything has gravity, no matter how small it is, no matter how large it is It all has gravity And then we’re going to be main sequence star Our sun is actually a rather small star in comparison to most of the other stars in the galaxy, in the universe Lots and lots of them are much, much bigger Now depending on the size of the star, they are going to undergo two different things Our sun, being a rather small star, once their nuclear fusion that goes on in the center has run out of fuel, it is going to become a red giant, and then it is going to cool down into a white dwarf or a black dwarf If it is a large star, much, much more massive than our sun, it is going to become a red supergiant It is going to undergo supernova, and then the dense, dense core of that is either going to turn into a black hole or a neutron star Now our sun is a second-generation star, because after this red supergiant undergoes supernova, what we are left with is a cloud of dust and gas And that cloud of dust and gas can get together again to form a new star And we know this, is ’cause the sun has heavy elements Things like iron are present in the center of the star, which means, since we were created from this cloud of dust and gas, which also formed the Earth, that you literally used to be a star You are a star You are made of stardust You are a star You can tell people that In the center of a star, we have loads of hydrogen and helium, and they’re going to be fusing together This is nuclear fusion, not fission that takes place in reactors that we have on Earth, but nuclear fusion, and we can see that massive amounts of energy is released And this is energy as light and as heat energy And if we were close enough, we would be able to get to hear the sound energy as well When all of the helium and hydrogen nuclei in the middle run out, that is when our star’s life comes to an end Now our star, our sun, is a main sequence star, so it’s going to have heavy elements as well They are going to be undergoing the same process, but the majority of elements inside a star, inside the majority of stars in the universe, are going to do hydrogen and helium An artificial satellite is going to be something that we’ve put up into space to orbit the Earth, whereas a natural satellite is going to be something like the moon, which naturally orbits the Earth A satellite is anything that orbits the Earth They maintain their orbit around the Earth due to gravity There is a key distinction between the term speed and velocity Speed is how fast you are going Velocity is how fast you are going in a certain direction So speed is going to be a scalar quantity

And velocity is going to be a vector quantity If something is going in a circle, for example, orbiting the planet, it can be going at a constant speed, but it is not going in the same direction If it was going in the same direction, it would always be going like that, in straight lines So it is constantly changing direction, which is why you can have a change in velocity while going at the same speed When we are looking at stars, we can see light coming from them And the wavelength of light can tell us things about them If the wavelength has increased, the frequency has decreased It means the wave is being stretched out It’s moving away from us When the wavelength is increased, the light coming from these stars is going to look red We can say this is red shifted Sometimes the light coming from these stars might look a bit blue When stars look a bit blue, it’s because the wave is being squashed It has a decreased wavelength and increased frequency That means that the star is coming towards us The majority of stars in the galaxy are moving away from us You’re gonna get maybe a dual system, where one is moving away from us, one is moving towards us So one might show a red shift, and one might show a blue shift But the majority are moving away from us And because they are moving away from us, we can make the reverse assumption that at one point they were closer to us, really close to us, or that at one point, they were in the same place as us And this is how red shift gives evidence for the Big Bang You are an absolute superstar for getting to the end of this video, well done All the best in your exams I’m keeping all my fingers and toes crossed for you Well done for making it to the end of the video I know that was a bit of a long slog But please remember just watching this video is not going to be enough to get you a fantastic grade If you really, really want to do well, you have to practice loads and loads and loads and loads, which means doing as many past papers as you can, which means doing as many questions from workbooks as you can It mean putting in lots and lots of hard work Just watching this video isn’t going to be enough I’ve done loads and loads of things to help you, over at my website, loads and loads of videos to help you In the revision guide, there are loads and loads of lists of things you need to know with links to videos if you can’t work it out for yourself But please, please, please, don’t think just watching this video is going to get you a fantastic grade You have to practice loads (gentle music)