0:00 hello lovelies in this video we're going to be going through the foundation content that you need for your AQA GCC physics paper 2 so this is really low key this is really chilled we're going to be taking it all step by step now once you've done this you can go to the website you can have look at the predicted papers and walkthroughs of the predicted papers that we've written for this [Music] [Applause] year in physics we learn about Scala and Vector quantities a Scala is a quantity which has magnitude only so it only has a size associated with it whereas the vector has both that magnitude but also Direction so in physics we might often
0:46 see vectors represented using an arrow and the size or length of that Arrow gives us an idea of the size of the quantity and the direction it's pointing tells us the direction of it now at gcsd of course we learn about so many different things now I've got this little table here just to summarize where certain things you've learned about are Scala and Vector so we need to know that speed is a Scala whereas velocity is a vector distance is a Scala whereas displacement is a vector time and energy are both scalar quantities as well because they just have a size associated with them not a direction whereas acceleration force and momentum all of these things we will
1:31 learn more about are all examples of vectors all forces are either contact forces or non-c contct forces contact forces are experienced when objects are physically touching some examples of this include friction where things are rubbing against each other air resistance where the air is in contact with you tension and also the normal contact force and there's loads of other ones too non-c contact forces on the other hand though involve objects that are not physically touching they're physically separated and yet they're still experiencing a force between them so some examples of this include magnetic forces if you've ever held two magnets together you'll be able to feel
2:16 even though they're not touching them pulling together or pushing apart even though there's no physical contact as well as this we have electrostatic forces and also gravitational forces now don't forget that Force whether we're talking about contact forces or non-c contct forces are vector quantities so they always have the magnitude or also the direction the weight of an object is the force acting on it caused by gravity that means that the weight of an object is dependent on the gravitational field strength in fact if we were to have our weight on planet Earth then we were taken to the moon or something which has a smaller gravitational field strength our weight would decrease we need to know that the weight
3:03 of an object is directly proportional to the mass of an object and the equation that links them is weight equals mass time gravitational field strength where weight is actually a force measured in Newtons Mass is measured in kilograms and G or gravitational field strength is measured in Newtons per kilogram now a really really common misconception and it's because of our everyday language is that our weight is the same as our Mass but it isn't it isn't at all and actually when we say that we weigh ourselves or we weigh this amount that's incorrect it's actually our mass that we are talking about so we need to get our head around the fact that in physics weight is the force in
3:50 Newtons if we want to measure the weight of an object we would use something called a Newton meter or a calibrated spring balance it's also important that we know that weight is considered to act at a single point the center of mass of an object lots of forces can act on an object however we can replace all of these different forces with just a single Force called the resultant Force now the resultant force is just a single force that has the same effect as all of the original forces acting together let's have a look at what that means so if we had a four Newton force and we added another four Newton force in the same direction to it there would be a
4:35 resultant force equal to eight Newtons in that same direction however if we had a six Newton force and it was encountering another 6 Newton Force but in the opposing Direction because force is a vector we could say that this is actually minus 6 Newtons what's going to happen then is these two forces are going to cancel each other out and so actually the resultant force is equal to zero make sure that you can do these yourself as well because they could ask very similar questions in the exam a force does work on an object when the force causes the object to move through a distance the work done by a
5:22 force on an object is given by work done equals force times by distance where work done is measured in Jews force is measured in Newtons and distance is measured in meters of course as always we could use a little cheeky triangle here if you struggle with the algebra if not I would always recommend that you just rearrange this using the algebra that you've learned in math but it's always good to have something up your sleeve in case you get stuck if you did use a triangle I would just pop a w on the top for work done and force times distance on the bottom now we need to know that one jewel is equal to 1 Newton met and this is because one Jewel of work is done when a force of one newton causes a
6:08 displacement of 1 meter it's also really important that we know that work done against friction will result in a temperature increase and this is why if you rub your hands together they start to get warm because you've done work against friction when a force acts on an object the object may bend contract or stretch or some combination of all of these changes to change the shape of a stationary object there must be more than one force acting on the object like you can see in these diagrams here so for example to swash a plastic bottle we must push the sides of the bottle together changes in shape are called defamation and we need to know about two types of defamation elastic and
6:54 inelastic now this table here summarizes the differences between those two elastic deoration is reversed when the force is removed for example an elastic band that gets slightly stretched would just ping back to its original shape when you remove the force elastic deformation on the other hand is not fully reversed when the force is removed and we see that there's been a permanent change in shape a good example of this is a plastic bottle that's been squashed or even perhaps an elastic band you stretch too far and now it's no longer stretching back the extension of an elastic object is directly proportional to the force applied to it provided that the limit of proportionality is not exceeded now this
7:41 is called hooks law the force applied to extend an elastic object by an extension e is given by force equals spring constant Time by extension or F = K * e where f is the force measured in Newtons K is the spring constant measured in Newtons per meter and E is the extension measured in meters now this relationship also applies to Springs that are compressed however in this case the E isn't going to be the extension it's going to be the amount that the object is compressed so now let's think if we plot Force against extension we will expect to see if Hook's laws being aade this direct proportion this straight line it
8:26 will go through the origin and it will have this constant gradient and in fact we can calculate the spring constant by finding the gradient of this line so the change in y over the change in X the limit of proportionality is the point at which Hook's law is no longer a bay and the extension is no longer directly proportional to the force applied now we can really clearly see this on a graph as you can see here in this graph you can see we've got a straight line for the first part of it so this region here however Beyond this limit of proportionality we no longer have that linear relationship between force and extension and that is when we know we have exceeded that limit of
9:11 proportionality so the elastic limit of a material is the furthest point it can be deformed and still be able to return to its original shape when that force is removed and when a material passes its elastic limit its deoration becomes inelastic when a spring is compressed by a force work is done on the spring and elastic potential energy gets stored in that spring now the elastic potential energy stored in a stretch spring is given by elastic potential energy equals half times the spring constant Time by extension squared or e e = a half * K * e^ 2 where our elastic potential energy is measured in jewles the spring
9:56 constant is measured in Newtons per meter and the extent is measured in meters now if the spring has no inelastic deoration we can say that the work done is equal to the elastic potential energy in physics we're going to see the words distance and displacement used really often however to you're everyday person you probably wouldn't think there's any difference between the two words however there is and we need to know that difference so distance is a measure of how far an object has moved however it gives us no information at all about the direction that the object has moved now for this reason distance is a scalar quantity displacement on the other hand tells us the distance an object has
10:41 moved but it also tells us the direction that it has moved in that means that displacement is a vector quantity speed is a scalar quantity that means that it does not have a direction the speed a person can walk or run depends on lots of different factors such as age Fitness distance traveled and terrain However unfortunately we need to know an approximate average speed for certain different activities we need to know that when walking the average approximate speed is 1.5 m/ second when running the average approximate speed is 3 m/s and cycling the average approximate speed is 6 m/ second so make sure you
11:29 learn those key facts the speed of sound and wind can also change dependent on the conditions we need to know that the typical speed of sound in air is 300 m/s the distance traveled by an object moving at a constant speed for a specific amount of time is given as distance traveled equals speed time time or S = V * T of course if you're not too confident you could always turn this into to a nice little triangle this is going to look something like this where the S is going to be on the top and then you have B * t on the bottom so long as you get the marks I am happy so remember distance is measured in meters velocity
12:16 is measured in me/ second and time is measured in seconds now velocity is a vector quantity velocity is just the speed in a given Direction if an object moves along a straight line the distance traveled can be represented by a distance time graph the gradient of that distance time graph gives us the speed of the object and if the graph shows a straight line like we can see in this diagram we know that the object is moving at a constant speed and the steeper the line the faster the speed however if the curve on the distance time graph slopes upwards and the gradient is getting steeper with
13:01 time we can see that the object is accelerating on the other hand if the curve on the distance time graph slopes downwards and it gets less steep over time then we can say that the object is decelerating average acceleration of an object can be calcula using acceleration equals the change in velocity over time taken we could see it written as a equals Delta Delta V where the Delta means change over T so the acceleration is measured in m/s squared the change in velocity is just measured in me/ second just like any old velocity and time is measured in seconds objects that are slowing down
13:47 are said to be decelerating and an object that is decelerating has negative acceleration remember acceleration is a vector the fact it can be positive or negative gives us that direction of the acceleration if an object moves along a straight line the velocity can be represented by a velocity time graph now the gradient of the Velocity time graph gives us the acceleration of the object if the graph shows a straight line then the object is moving at a constant acceleration and of course the steeper the line the greater the acceleration because we've got this larger gradient for steeper lines now if the curve and a velocity time graph is curved then the object's acceleration is
14:33 changing if however we have a horizontal line on a velocity time graph then that tells us the object has constant velocity if an object moves through a fluid a gas or a liquid initially it's going to accelerate just due to the force of gravity however as it falls resisted forces will start to increase until eventually that force of gravity the weight will become balanced with the those resistive forces this means that there's no overall force no resultant force and terminal velocity has been reached now all the terminal velocity means is it's that constant velocity it is now falling under so make sure that you familiarize yourself with this phrase of terminal velocity and you
15:20 understand what it means Newton's first law states that if the resultant force on a stationary object is zero the the object will remain stationary however if the resultant force on a moving object is zero the object will continue moving in the same direction with the same speed when we have an object moving at a constant speed the driving force will be balanced by resistive forces such as the friction and the air resistance that's what gives it that resultant force of zero because they're balanced and therefore it just continues in the same direction ction with the same speed according to Newton's first law Newton's Second Law tells us that
16:05 the acceleration of an object is directly proportional to the resultant force acting on the object and inversely proportional to the mass of the object now as a little top tip make sure that you remember that this symbol here represents proportionality looks a bit like little fish and this like squiggly equal sign means approximately now Newton's second laog gives us this very important equation resultant Force equals mass time acceleration or F = M * a remember we could use a triangle if you find it difficult to rearrange these equations anything that's going to get you the marks if we did use the triangle for this then we would put the F on the top and the M * a on the bottom don't
16:53 forget that force is measured in Newtons Mass is measured in kilogram and acceleration is measured in m/s squared Newton's third law tells us that when two objects interact forces that they exert on each other are equal in magnitude and opposite in direction so here let's have a look at this diagram here A man is pushing on a wall so he's got the force of his push however the wall is going to exert an equal and opposite Force back on that man and that is showing us Newton's Third stopping distance is the sum of the thinking distance and the breaking distance so it's the distance in total that it takes for you to stop from the
17:40 moment you see an object to the moment you stop okay so the thinking distance is the distance that the travel thinks during the driver's reaction time so imagine you're driving along and you see a rabbit run into the road the thinking distance will be the distance that you travel between the moment you see that rabbit to the moment you put your foot on the brake and then the braking distance is the distance the vehicle travels under the braking Force so that is the distance you travel from the moment you put your foot on the pedal to the moment you're stationary so for a given braking force greater speed is going to cause greater stopping distances the typical reaction time of a person is between 0.2 seconds and 0.9
18:28 seconds make sure you learn that fact now there's a few things that can affect the reaction time of a driver and therefore the thinking distance traveled the reaction time can get affected by tiredness the more tired you are the longer your reaction time the use of drugs the use of alcohol and also the presence of distractions so for instance loud music things like this can distract you and increase the reaction time of the driver we need to be able to describe a method to measure human reaction times so here we go okay so first up ask a person to sit at a desk with their hand out hold a ruler up to their hand and line up the zero on the ruler with the
19:15 person's thumb and forefinger so now you're going to tell the person that when the ruler gets released they need to catch it as quickly as possible so now we're going to drop that ruler but we're not going to tell the person and we're going to measure the distance traveled by the ruler in this time before they can stop the ruler so now we have enough information to calculate the final velocity of the ruler we can use the equation for constant acceleration that states that V ^2 = U ^2 + 2 a s we know that U is equal to zero because it started stationary s is the distance traveled by the ruler that we measured and a is the acceleration caused due to gravity which we could use 9 .8 m/s squar or 10 m/s
20:02 squar a question would give you a number to use if you needed it so now you're going to use that equation to find V and once you know what V is you can calculate the time taken using the equation that says the acceleration equals change in velocity over time of course we'll need to rearrange it to get time as the subject time would be equal to change in velocity over acceleration well once we've done that we can just substitute the values that we already know to get that time so once we do that we will finish off by carrying out some repeats and calculate a being to ensure this experiment is calculated correctly and we're actually just working out those human reaction times we need to make sure that we carry this out in a room with no distractions
20:49 that's going to affect that reaction time the braking distance of a vehicle is affected by the road and weather conditions so if we have poor Road and weather conditions such as icy or wet roads we're going to increase the braking distance braking distance also effects on the vehicle conditions so if we have poor vehicle conditions such as worn tires or worn brakes again we're going to increase the braking distance of the vehicle now velocity also affects braking distance and we need to know very particularly if velocity doubles the stopping distance actually increases by a factor of of four it doesn't just double two it increases by a factor of four so make
21:34 sure you know that now when a force gets applied to the brakes of a vehicle work is done now the friction between the tires and the brake pads causes the kinetic energy of the vehicle to decrease and the brake pads to increase in temperature ultimately the faster the vehicle travels the greater the braking Force required and therefore the greater deceleration that we have now of course we need to know what is dangerous about a greater deceleration we need to know that the brakes can overheat under these conditions and the driver may lose control of the vehicle so make sure you know those dangers [Music]
23:16 waves can be described as oscillations or vibrations about a point the direction of the vibration can differ and this is what determines the type of wave waves can be transvers or longitudinal and in a transverse wave the vibrations are at right angles to the direction in which the waves transfer energy however with a longitudinal wave the vibrations are parallel to the direction in which the waves transfer energy now this can be a bit confusing If instead we think of it in terms of a long spring like a slinky and we think what can we do with this Slinky to turn it into a transverse wave or a longitudinal wave and if we wanted to make a transverse wave we would want to take that Slinky
24:03 and move it up and down and up and down and up and down now if you think about it the waves are moving forward but the vibrations your hand are at right angles to that forward Direction longitudinal waves on the other hand if you had that same spring or Slinky and you wanted to make a longitudinal wave you would bump it back and forth with your hand and there your vibration that movement of your hand is parallel to the direction in which the waves transfer energy now for ripples on the surface of water and sound waves in air we need to know that it's not the water or the air that's traveling it is the wave so if we think for example about a stone that is
24:48 dropped into water we can see that ripples are produced however neither the water nor the stone move with the ripples it's just the wave if we also think about someone speaking in this case the voice box will be vibrating making sound waves that will travel through the air however that air is not moving we need to ensure that we can label a transverse wave and recognize its shape so the transverse wave as you can see here looks like your very typical wave up and down and up and down now the tops of each of these waves is called Peak the B bottoms are called the trough the height from the equilibrium position
25:33 to the peak or the trough is called the amplitude make sure that you don't say it's from the peak to the trough that's a very common mistake and the wavelength is the distance between two identical points on the wave now an easy way to do this is going from Peak to Peak or tro to tro so here another wavelength that we could draw on would be this position here it is identical to the wavelength labored on this diagram but perhaps it's an easy way to identify it so some mechanical waves are transverse for example water waves and seismic S waves in addition to this all of the electromagnetic waves that we will learn about in more detail for example
26:20 ultraviolet and infrared are all transverse now longitudinal waves look like this long Udin waves have compressions which are regions of high pressure where the particles are close together and they also have rare factions which are regions of low pressure where the particles are far apart now we'll find that some mechanical waves are longitudinal these include sound waves ultrasound and also seismic p waves we need to make sure that we can describe waves in the following terms we need to make sure that we know that amplitude is is the maximum displacement of a point on a wave from its rest position the period is the time it takes for a wave to complete one
27:06 cycle wave speed is calculated using wave speed equals frequency time wavelength frequency is the number of waves passing a point per second and wavelength is the distance between a point on one wave and the next point on the same wave now wave speed is the speed at which energy is transferred through a medium and as we've seen we can calculate this using the following equation wave speed equals frequency Time by wavelength or v = f * Lambda where Lambda is a Greek symbol used to represent the wavelength now wave speed is measured in me/ second frequency is measured in hertz and wavelength is measured in
27:52 meters now if you're doing physics instead of combined science we also need to know that when waves travel from one medium to another the wave speed and the wavelength may change but the frequency will always stay the same the period of a wave can be calculated using the frequency of the wave so period is equal to 1 over the frequency this can be written as T = 1 / f don't forget that the period is the time it takes for a wave to complete one cycle so period is measured in seconds whereas the frequency is measured in hertz it's also important that you remember that we might need to find the frequency given the time period now if
28:40 this was to occur we would simply rearrange the equation and this would look like f = 1 / T So a really easy one to rearrange there and we might be asked how to measure the velocity of sound in air now experiment that we could do to do this would be to have two people stand a large distance apart for instance 100 m use a trundle wheel to measure that distance between them because it's too large to use the meter Rule now get one of these people to make a loud noise so perhaps they could bang together two wooden blocks or bang together some symbols and the other person is going to have a stopwatch and you're going to ask this person to start the stopwatch when they see the person make the noise and
29:27 then stop it when they actually hear it then we're going to repeat this experiment and take an average take the mean we're going to use the following equation now to calculate the speed of sound in air so we know that wave speed is equal to distance which could be that 100 m and then we divide it by that mean time that we calculated it takes for the person to hear the noise we could also be asked how to measure the velocity of ripples on water surfaces so to do this set up a ripple tank and add water to it to a depth of about 5 cm now we want to adjust the height of the wooden rod so that it is just touching the surface of the water now
30:15 we're going to turn on the motor and the lamp so that we can observe low frequency waves now we want to measure the length of several waves and divide by the number of waves to find the wavelength this is going to be more accurate than just measuring one wave now we want to count the number of waves that pass a point in 10 seconds and divide by 10 to find the frequency finally we can use the equation that wave speed equals frequency times by wavelength to calculate the wave speed electromagnetic waves are transverse waves that transfer energy they form a continuous Spectrum which means that they're just one giant range of waves with varying wavelengths
31:02 and frequencies as you can see down here in this diagram we've got this long wave which goes from radio wave to microwave to infrared to visible light to ultraviolet to x-rays to gamma rays now we need to know these in order okay now there's a neonic that can help us do this there's loads of neonics actually I'm going to give you one but by all means make your own or find one that you really like I like to use this one which is that rabbits meet in very Ultra expensive Gardens absolute nonsense but if it can help place our different electromagnetic waves in order then that's all I care
31:48 about we need to know that the radio waves here have the longest wavelength the lowest frequency and the lowest energy of all of these waves whereas on the other end of this spectrum the gamma rays we have the shortest wavelength the highest frequency and the highest energy so make sure that you learn all of these and you know their properties you know that they're transverse waves they transfer energy and they all travel at the same velocity through a vacuum or air electromagnetic waves can be refracted when they move from one substance to another this means that the wave changes direction we can use Ray diagrams like
32:33 the one you can see here to show the refraction of a wave at the boundary between two substances electromagnetic waves can be generated or absorbed because of changes in atoms and the nuclei of atoms when the electrons in an atom will move down energy levels as you can see in this diagram they will emit electromagnetic waves now some electromag itic waves are more hazardous than others for instance UV rays X-rays and gamma rays can all have hazardous effects on human body tissues the effect that they will have depends on the type of the radiation and the size of the radiation dose radiation dose is a measure of the risk of harm resulting from an exposure
33:19 of the body to the radiation radiation dose is measured in CTS and we should know that 1,000 M CTS is equal to to one cver because we'll often have to convert between the units electromagnetic waves become more dangerous as the frequency of the wave increases this table here shows some of the potential dangers that we need to know so we need to know that microwaves can cause the internal heating of body cells we need to know that infrared can cause skin burns ultraviolet can cause damage to surface cells leading to skin cancer caner as well as premature aging it can also cause damage to the eyes leading to eye
34:04 conditions now x-rays can cause mutations and damage to body cells again and gamma rays can also cause mutations and damage to body cells we need to know the uses of our different types of electromagnetic radiation so radio waves can be used for broadcasting satellite transmissions and Communications microwaves can be used for cooking also satellite transmissions and Communications infrared can be used for cooking thermal imaging and also short range Communications then we get to visible light which includes of course the red orange yellow green blue indigo violet colors this is used for vision and also for
34:50 photography ultraviolet now is used for security marking fluorescent lamps and also dis infecting water x-rays are used to observe the internal structure of objects we can have medical X-rays and also airport security scanners gamma rays on the other hand are used for sterilizing food and medical equipment because they're able to kill bacteria they can also treat and detect cancer [Music]
36:21 this topic starts nice and simple we remind ourselves that magnets have North and South Poles North Poles get represented Ed by an n and South Pole is represented with an S we should know that magnets will attract magnetic materials such as iron steel Cobalt and nickel we should know that like poles will repel and different poles attract and of course don't forget that magnetic forces are examples of non-con forces permanent magnets produce their own magnetic field which will always be there induced magnets however become magnetic in a magnet magnetic field well what is a magnetic field that we're talking about so we're going to use this concept A Lot in this topic a magnetic field is a region around a
37:07 magnet where a magnetic material or another magnet will experience a force and we represent these magnetic fields using magnetic field lines we need to be able to draw and recognize the magnetic field pattern around a bar magnet this diagram here shows it perfectly so we will see that magnetic field lines will always point from north to south this is really important the closer the field lines the stronger the field and the magnetic field strength you'll notice certainly because they're closer together in this diagram is that it's strongest near the poles as we move away from the magnet the magnetic field strength decreases in the exam we might be asked how to plot a magnetic field and we can
37:52 do this using magnetic compasses so our first step is you're going to place the compasses around your magnet on a piece of paper we will then Mark the direction that the needle points onto the paper and then finally We join these points together and this will show the field lines magnetic compasses that we used to work out Direction actually contain a small bar magnet and when these magnetic compasses are not near to another magnet they're actually going to line up with the magnetic field of the earth and this is really important because this tells us that the Earth has a magnetic core it tells us that it's made of a material which is magnetic now actually the geographical
38:39 South Pole of the earth is actually the Magnetic North Pole and vice versa when a current flows through a conducting wire a magnetic field gets produced around that wire as you can see in these diagrams they form little concentric circles around that wire and the strength of the magnetic field that gets made depends on the size of the current Going Through the Wire the bigger the current the bigger that magnetic field and also the distance from The Wire the closer to the wire that's stronger that magnetic field and the further away you get the weaker it becomes we can also increase the strength of the magnetic field made by a Wire by curling it into a solenoid which
39:24 looks just like this the maget magnetic field around a solenoid actually ends up being very similar to the magnetic field around a bar magnet the diagram here shows what that magnetic field around a solenoid looks like you can see that inside the solenoid it is strong and uniform we can see it's uniform because the magnetic field lines look evenly spaced and we can also see that they're close together inside that solenoid which is what shows that it's strong the magnetic field is stronger inside the solenoid compared to outside because all of the small magnetic fields caused by the current in each of those turns will add up causing a greater overall magnetic field if we wanted to increase
40:11 the strength of the magnetic field around a solenoid even more we can add an iron core and this makes an electromagnet you may be asked an exam what are some advantages of electromagnets compared to other magnets so one of the really important differences is that we can switch electromagnets on and off simply by turning that current on and off now you might think why would this be useful but if we look at the diagram here imagine we're in some scrapyard or we're moving around old scrap cars or something it's much easier if we can use this magnetic force turn on the electromagnet attract our magnetic materials and move them using that force and then turn it off and release them
40:58 another great advantage of electromagnets is that the strength of the electromagnet can be adjusted simply by changing the current if we increase the current we get a stronger electromagnet whereas if we have a permanent magnet the strength of that magnet is just the strength of that magnet we might see some applications of electromagnets come up in the exam so let's have a look at this specific example of an electric Bell and let's see how electromagnets can work now looking at this if we close the switch we will turn on the electromagnet because the current can flow through the circuit of course looking at the diagram you can see we've got this iron Armature this is going to get attracted to the electromagnet and this is going to pull
41:43 the hammer towards the bell and they're going to hit each other and it's going to sound the Bell however of course when this happens we've broken the circuit and that turns off the electromagnet this means that the arm is no longer retracted towards the magnet and it's going to move back to its original position but by moving back to its original position it's completed the circuit again and so we're going to have this process just go back and forth back and forth back and forth on repeat sounding that Bell now this is one application we could see loads of other ones too so we just need to make sure that we can apply these principles to any little example they might give us ouch
42:30 this is why in some videos I explain scratches [Music]
