AS Level Physics Lecture Notes

foreign [Music] physics right and uh and as you can see here these are the topics of your as level physical quantities and units you have kinematics you have Dynamics you have forces density and pressure [Music] you have work energy and power deformation of solids waves superposition electricity DC circuits and particle physics right so these are the topics that you'll be studying in as and uh you'll be able to appear in three papers in as and two papers a day to paper one multiple choice paper two is level structured questions and paper three is Advanced practical skills I'll make a separate video for that that what are the techniques for each of these papers right uh so today what we're going to talk about is the physical quantities and units right so we'll talk about understand it all physical quantities they consist of a numerical magnitude in a unit right uh and after that we'll move towards the SI units before starting uh estimation we'll talk about that these are the following SI based quantities which are mass length time current temperature and we'll talk about their units right then we'll talk about derived units and what are the derived units they are the products or quotients of the SI base units and they can be used to derive you know quantities listed in the syllabus then we'll talk about the homogeneous equations and then we'll talk about the prefixes such as Pico Nano micro Milli centi Desi kilo Mega Giga enter right so we'll talk about these things and then we have errors and uncertainties and scalars and vectors right so let us begin you should know that all physical quantities they consist of a numerical magnitude and a unit So Physical quantities what you do is they consist of a magnitude in the unit for example length is a physical quantity and remember that that for example lint has a magnitude for example it is 6.0 meters as you can see here now 6.0 is what it is the numerical magnitude and meter here is the unit for that so what is a physical quantity a physical quantity foreign of a numerical magnitude and a unit remember that a physical quantity consists of a numerical magnitude and a unit for example we have various basic physical quantities and they are for example Mass what is the SI unit for mass Mr kilogram and we can write here the symbol for kilogram as kg we have length so the SR unit for length is what it is meter and we can write here meter right small m then we have time and that is second that goes with a small s here and then we have the temperature which is in Kelvin and this is what capital K Kelvin right we have another physical quantity here that is that is the electric current that is ampere capital a so these are the five basic physical quantities that you will study in as level syllabus A1 apart from that there's another physical quantity and that is the amount of substance and the SI unit for that is mole right and the unit the symbol for that is Mom you see the symbol is mol and the SI unit is mole right the symbol for that is mole is that clear now I'm going to talk about the derived quantity so what does a derived quantity remember that a derived quantity is related to the base quantities through a defining equation and what it means is that a derived quantity can be expressed it can be expressed as the product or quotient of the base quantities what I mean here is that that the derived qualities they go back to these five basic physical quantities and they're composed of these for example we have here density now you know that density is mass per unit volume right and as you can see here the unit the SI unit for mass is kilogram the volume is for example uh in SI unit it's going to be meter cube yes because the unit of length SI unit for length is meter so CM cube is another unit that's not an SI unit so we have volume as length into width into height for example so this is in meters this is in meters this is the meters and this goes to intercube so the SI unit for density becomes here kilogram M minus 3. so you have seen here one important thing that the kilogram here goes to this mass and meter cube is in fact composed of the length meter into meter into meter so this is a derived quantity now similarly we have acceleration you know that acceleration is what that is the final velocity minus the initial velocity over time and you can write here V minus U over delta T where delta T is the time right and you know that this can be written as Delta V over delta T now you should know that what is Delta V Delta V is the rate yeah that is the rate of change of displacement velocity is the rate of change of displacement so it is going to be what so the units are there are meter per second and you have here time which is also in seconds so this becomes meter per second Square this goes up so you see that this is again a derived unit it is composed of the length and it is composed of the time it goes back to the basic physical confidence right clear there is another example here a very very common that is force so if we have Force what are the SI base units for force so you have mass times the acceleration and you know that the mass is in kilograms an acceleration is in meter per second Square so the SI unit for uh the force becomes kg meter per second Square as simple it is we have another quantity which is known as power power is that Newton is just an SI unit s i base units are this it's very good question Newton is only the SI unit these are the SI base units so in fact one newton is equal to this one newton is in fact equal to this Newton is just an SI unit these are the SI base units whenever they are asked you to find the SI base units you have to go back to these five basic physical quantities is that clear okay then we have power power is what it is the rate of work done rate of work that means that the time is involved already and we will do that later on in the future as well right in the topic of work energy and power so power is work done over time and you should know that that the work done is force into distance over time and for the force it becomes kg meter per second Square for distance it becomes meter for time it is seconds and this becomes kg meter Square s minus 3. so there you go right you figured out the units of the SI based units of power and in fact this is equal to one volt since you know that SI unit for power is what which is one joule per second right pressure here pressure is force over area and you will apply the same strategy as you did here in order to calculate the SI base units for the pressure now the SI unit for pressure is what that is Pascal but the SI based units or what [Music] that is kg meter per second Square over meter Square this goes up [Music] minus one very good this is minus two since two when it goes upstairs it becomes minus two so minus 2 plus 1 is minus 1 and then we have S minus 2. so I hope that this is how you will do it there's a very good past paper question here let's do one of the passwords question here right so you have here a question from Winter 18 paper one two and they've asked you to find out the SI base units of resistance so what will you do here you have been given the what what is the unit of resistance when expressed in SI base units so what you'll do is you know that that R is V over I where V is what V is the potential difference I is the current and R is the resistance now you know that the potential difference V can be written as worked on per unit charge foreign charge and the work done is Force into distance the charge is i t [Music] we can write here kg meter per second Square into distance which is in meters the current is an ampere time is in seconds and you get what you get kg meter Square this s goes upstairs this becomes s minus 3 a minus 1. so these are the units of the potential s i base units of potential and the units of resistance are going to be kg meter Square s minus 3 a minus 1 and you have here ampere this goes upstairs again you have kg meter Square s minus 3 a minus 2. so the answer is B this is how you will do it right SI base units of resistance are kg meter Square s minus 3 A minus 2. I hope this is clear right now we have some questions which are with no units we're going to talk about them there are some questions which have no units and we call them dimensionless constructs for example and remember that these are constants which have no units at all these are constraints which have no units for example you have here the refractive index now refractive index is the ratio of sine of angle of incidence over sine of angle of refraction now if you look closely sine is what sine is the ratio of opposite over hypotenuse if you have a triangle like this for example it's a right angle triangle this angle for example is Theta you know that sine Theta is opposite if this is the opposite and if this is the hypotenuse you see both of them are lengths so for example this is in meters this is also in meters they're going to cancel out right so sine I itself has no units sine R itself has no units so refractive index will also have no units so refractive index is what it is a dimensionless constant similarly we have there is another formula for this n is equal to C over V now as you can see here C is the speed of light in vacuum it's in meter per second V is the speed of light in that particular medium for example it is also meter per second so again you see that they both cancel out so again refractive index has no unit there's another thing that you will study later on in the topic of deformation that is topic number six of your as11 syllabus and uh in that case for example you have a spring here and it has original length that is n the spring here has the original length which is this for example you apply a load here so that it extends for example you apply a load so there is a force that is applied here and it extends here the extension here is X for example X is the extension now there's a quantity that you can study in topic six that is known as strain The Strain is given by the formula extension over original length so this extension here is I'm going to write it like this X over n for example extension is in millimeters the length is also in millimeters for example right both are the lens they cancel out and strain has no units right so strain is again a dimensionless constraint is and there are other dimensionless constants for example pi why is the dimensionless constant all real numbers they are dimensionless constants right like one two three four five they're all dimensionless concentrate so there is a very uh very good question in the examination we're going to do a possible question now right uh so there's a very good question regarding the the dimensionless constants here this is from November 16 paper 1 2 right and we have here a question the speed of sound in a gas is given by the equation V is equal to square root of gamma p over rho where p is the pressure of the gas rho is the density and Gamma is a constant what are the SI base units of gamma so you have to solve this equation so what you'll do here is first of all whenever you have such sort of questions what you do is you make that constant the subject so I'm going to make gamma the subject here what I'm going to do is I have V here I'm going to take the square here and I have square root of Sigma p over a gamma p over rho and I'm going to take the square square here right what is the purpose of the square this will eliminate this under root this under root would be eliminated this becomes V squared Sigma p over rho and I'm gonna make this uh this Gamma or the subject right this is gamma in fact this is V Square V Square rho over P now what I'm going to do is I'm going to put in the values here so gamma is here V is what that is meter per second whole Square this row here is what that is the density that is kilogram M minus 3 kilogram per meter cube pressure is rho g h pressure is hydrostatic pressure is rho G Delta H right where rho is the density G is the gravitational acceleration and H is the depth so I'm going to write here in in place of rho I'm going to write here kg M minus 3 G is meter per second Square H is in meters now this this cancels with this one and I have meter Square s minus 2 this power goes here in and we have here meter Square s minus 2. now what happens this s minus 2 and S minus 2 they get canceled out this meter Square this meters will get gets canceled out and this gives us no you're right so this is the answer for this question right I hope this is clear to all of you

foreign [Music] physics right and uh and as you can see here these are the topics of your as level physical quantities and units you have kinematics you have Dynamics you have forces density and pressure [Music] you have work energy and power deformation of solids waves superposition electricity DC circuits and particle physics right so these are the topics that you&#39;ll be studying in as and uh you&#39;ll be able to appear in three papers in as and two papers a day to paper one multiple choice paper two is level structured questions and paper three is Advanced practical skills I&#39;ll make a separate video for that that what are the techniques for each of these papers right uh so today what we&#39;re going to talk about is the physical quantities and units right so we&#39;ll talk about understand it all physical quantities they consist of a numerical magnitude in a unit right uh and after that we&#39;ll move towards the SI units before starting uh estimation we&#39;ll talk about that these are the following SI based quantities which are mass length time current temperature and we&#39;ll talk about their units right then we&#39;ll talk about derived units and what are the derived units they are the products or quotients of the SI base units and they can be used to derive you know quantities listed in the syllabus then we&#39;ll talk about the homogeneous equations and then we&#39;ll talk about the prefixes such as Pico Nano micro Milli centi Desi kilo Mega Giga enter right so we&#39;ll talk about these things and then we have errors and uncertainties and scalars and vectors right so let us begin you should know that all physical quantities they consist of a numerical magnitude and a unit So Physical quantities what you do is they consist of a magnitude in the unit for example length is a physical quantity and remember that that for example lint has a magnitude for example it is 6.0 meters as you can see here now 6.0 is what it is the numerical magnitude and meter here is the unit for that so what is a physical quantity a physical quantity foreign of a numerical magnitude and a unit remember that a physical quantity consists of a numerical magnitude and a unit for example we have various basic physical quantities and they are for example Mass what is the SI unit for mass Mr kilogram and we can write here the symbol for kilogram as kg we have length so the SR unit for length is what it is meter and we can write here meter right small m then we have time and that is second that goes with a small s here and then we have the temperature which is in Kelvin and this is what capital K Kelvin right we have another physical quantity here that is that is the electric current that is ampere capital a so these are the five basic physical quantities that you will study in as level syllabus A1 apart from that there&#39;s another physical quantity and that is the amount of substance and the SI unit for that is mole right and the unit the symbol for that is Mom you see the symbol is mol and the SI unit is mole right the symbol for that is mole is that clear now I&#39;m going to talk about the derived quantity so what does a derived quantity remember that a derived quantity is related to the base quantities through a defining equation and what it means is that a derived quantity can be expressed it can be expressed as the product or quotient of the base quantities what I mean here is that that the derived qualities they go back to these five basic physical quantities and they&#39;re composed of these for example we have here density now you know that density is mass per unit volume right and as you can see here the unit the SI unit for mass is kilogram the volume is for example uh in SI unit it&#39;s going to be meter cube yes because the unit of length SI unit for length is meter so CM cube is another unit that&#39;s not an SI unit so we have volume as length into width into height for example so this is in meters this is in meters this is the meters and this goes to intercube so the SI unit for density becomes here kilogram M minus 3. so you have seen here one important thing that the kilogram here goes to this mass and meter cube is in fact composed of the length meter into meter into meter so this is a derived quantity now similarly we have acceleration you know that acceleration is what that is the final velocity minus the initial velocity over time and you can write here V minus U over delta T where delta T is the time right and you know that this can be written as Delta V over delta T now you should know that what is Delta V Delta V is the rate yeah that is the rate of change of displacement velocity is the rate of change of displacement so it is going to be what so the units are there are meter per second and you have here time which is also in seconds so this becomes meter per second Square this goes up so you see that this is again a derived unit it is composed of the length and it is composed of the time it goes back to the basic physical confidence right clear there is another example here a very very common that is force so if we have Force what are the SI base units for force so you have mass times the acceleration and you know that the mass is in kilograms an acceleration is in meter per second Square so the SI unit for uh the force becomes kg meter per second Square as simple it is we have another quantity which is known as power power is that Newton is just an SI unit s i base units are this it&#39;s very good question Newton is only the SI unit these are the SI base units so in fact one newton is equal to this one newton is in fact equal to this Newton is just an SI unit these are the SI base units whenever they are asked you to find the SI base units you have to go back to these five basic physical quantities is that clear okay then we have power power is what it is the rate of work done rate of work that means that the time is involved already and we will do that later on in the future as well right in the topic of work energy and power so power is work done over time and you should know that that the work done is force into distance over time and for the force it becomes kg meter per second Square for distance it becomes meter for time it is seconds and this becomes kg meter Square s minus 3. so there you go right you figured out the units of the SI based units of power and in fact this is equal to one volt since you know that SI unit for power is what which is one joule per second right pressure here pressure is force over area and you will apply the same strategy as you did here in order to calculate the SI base units for the pressure now the SI unit for pressure is what that is Pascal but the SI based units or what [Music] that is kg meter per second Square over meter Square this goes up [Music] minus one very good this is minus two since two when it goes upstairs it becomes minus two so minus 2 plus 1 is minus 1 and then we have S minus 2. so I hope that this is how you will do it there&#39;s a very good past paper question here let&#39;s do one of the passwords question here right so you have here a question from Winter 18 paper one two and they&#39;ve asked you to find out the SI base units of resistance so what will you do here you have been given the what what is the unit of resistance when expressed in SI base units so what you&#39;ll do is you know that that R is V over I where V is what V is the potential difference I is the current and R is the resistance now you know that the potential difference V can be written as worked on per unit charge foreign charge and the work done is Force into distance the charge is i t [Music] we can write here kg meter per second Square into distance which is in meters the current is an ampere time is in seconds and you get what you get kg meter Square this s goes upstairs this becomes s minus 3 a minus 1. so these are the units of the potential s i base units of potential and the units of resistance are going to be kg meter Square s minus 3 a minus 1 and you have here ampere this goes upstairs again you have kg meter Square s minus 3 a minus 2. so the answer is B this is how you will do it right SI base units of resistance are kg meter Square s minus 3 A minus 2. I hope this is clear right now we have some questions which are with no units we&#39;re going to talk about them there are some questions which have no units and we call them dimensionless constructs for example and remember that these are constants which have no units at all these are constraints which have no units for example you have here the refractive index now refractive index is the ratio of sine of angle of incidence over sine of angle of refraction now if you look closely sine is what sine is the ratio of opposite over hypotenuse if you have a triangle like this for example it&#39;s a right angle triangle this angle for example is Theta you know that sine Theta is opposite if this is the opposite and if this is the hypotenuse you see both of them are lengths so for example this is in meters this is also in meters they&#39;re going to cancel out right so sine I itself has no units sine R itself has no units so refractive index will also have no units so refractive index is what it is a dimensionless constant similarly we have there is another formula for this n is equal to C over V now as you can see here C is the speed of light in vacuum it&#39;s in meter per second V is the speed of light in that particular medium for example it is also meter per second so again you see that they both cancel out so again refractive index has no unit there&#39;s another thing that you will study later on in the topic of deformation that is topic number six of your as11 syllabus and uh in that case for example you have a spring here and it has original length that is n the spring here has the original length which is this for example you apply a load here so that it extends for example you apply a load so there is a force that is applied here and it extends here the extension here is X for example X is the extension now there&#39;s a quantity that you can study in topic six that is known as strain The Strain is given by the formula extension over original length so this extension here is I&#39;m going to write it like this X over n for example extension is in millimeters the length is also in millimeters for example right both are the lens they cancel out and strain has no units right so strain is again a dimensionless constraint is and there are other dimensionless constants for example pi why is the dimensionless constant all real numbers they are dimensionless constants right like one two three four five they&#39;re all dimensionless concentrate so there is a very uh very good question in the examination we&#39;re going to do a possible question now right uh so there&#39;s a very good question regarding the the dimensionless constants here this is from November 16 paper 1 2 right and we have here a question the speed of sound in a gas is given by the equation V is equal to square root of gamma p over rho where p is the pressure of the gas rho is the density and Gamma is a constant what are the SI base units of gamma so you have to solve this equation so what you&#39;ll do here is first of all whenever you have such sort of questions what you do is you make that constant the subject so I&#39;m going to make gamma the subject here what I&#39;m going to do is I have V here I&#39;m going to take the square here and I have square root of Sigma p over a gamma p over rho and I&#39;m going to take the square square here right what is the purpose of the square this will eliminate this under root this under root would be eliminated this becomes V squared Sigma p over rho and I&#39;m gonna make this uh this Gamma or the subject right this is gamma in fact this is V Square V Square rho over P now what I&#39;m going to do is I&#39;m going to put in the values here so gamma is here V is what that is meter per second whole Square this row here is what that is the density that is kilogram M minus 3 kilogram per meter cube pressure is rho g h pressure is hydrostatic pressure is rho G Delta H right where rho is the density G is the gravitational acceleration and H is the depth so I&#39;m going to write here in in place of rho I&#39;m going to write here kg M minus 3 G is meter per second Square H is in meters now this this cancels with this one and I have meter Square s minus 2 this power goes here in and we have here meter Square s minus 2. now what happens this s minus 2 and S minus 2 they get canceled out this meter Square this meters will get gets canceled out and this gives us no you&#39;re right so this is the answer for this question right I hope this is clear to all of you

Transcript for:AS Level Physics Lecture Notes

Transcript for:
AS Level Physics Lecture Notes