in this video we will do a quick revision for the topic motion forces and energy in IGCSE 0625 physics syllabus so here the first topic is motion forces and energy where we need to study physical quantities and measurement techniques so first we can see what are the physical quantities mentioned in the syllabus and which are the measuring devices we can use so the first physical quantity is length and length can be measured using a ruler you don't have to study about Vernier caliper or screw gauge because it is removed from the latest syllabus next volume volume can be measured using a measuring cylinder then different time intervals time intervals can be measured using clocks and digital timers so you should be familiar with these physical quantities and how we can measured using these devices next when we measure the volume there are different methods that is first if you have a irregular shaped object or if you have a regular shaped object in both case measuring the volume is different if you have a irregular shaped object we will use measuring cylinder how can we use measuring cylinder so here we can consider we have a stone which is not having a regular shape so what we have to do is as mentioned we can use a measuring cylinder here so first take a measuring cylinder using machine cylinder we can measure the volume of liquid we know that and which should be filled with a liquid now initially measure the volume that is initial volume we can represent as V1 then later what we have to do is we have to immerse this object which is having a irregularly shaped irregular shape so that we can measure the volume of this object when we dip this object in the liquid we know that the water level will increase so the water level will rise so we will get a new volume we can represent this one V2 so the volume of the irregularly shaped object will be the difference of these two volume that is the final volume of the liquid minus initial volume of the liquid but if you are having object which is having a regular shape for example a cuboid that is having a regular shape so we can use the formula to calculate the volume a cuboid will have a length this side is breadth and it will have height so the volume can be measured using the equation LBH so for an object which is having a regular shaped object you can use water displacement method and for a regular shaped object in order to calculate volume you can use the formula next topic is determine an average value from multiple reading this is also very important topic so the value of multiple reading will be given for example first one the thickness so the thickness of multiple objects will be given for example that the total thickness of stack of papers will be given so the total disc thickness Let It Be X that is nothing but total thickness and number of pages will also given Let It Be Y and you need to calculate what is the thickness of a single page so in this kind of question we have to divide as you need to calculate the thickness you should write the thickness at the numerator so the total thickness divided by number of pages always write the number at the denominator students get confused they get confused to whether right number of pages at the top or bottom always write number at the bottom or at the denominator measuring the time period of a simple pendulum is also coming in this tab topic under this topic so how to measure the time period of a pendulum so first we can see what is pendulum pendulum is a bob connected to a thread and which is connected to a fixed end so that it is free to move like this it can oscillate and one oscillation means if you are considering these as the starting position it will go to the one extreme position and it come back to its initial position and it will go back go to The Other Extreme position and come back to the initial position this movement is one oscillation so the time taken for this one oscillation is known as time period which is represented by capital T So time period T of a symbol pendulum is nothing but the time taken for one complete oscillation in order to get an accurate value instead of measuring one oscillation time we can measure the time for 10 or more oscillations then we can find the average time or time for one oscillation this is how we usually you do so as a formula we can write down time period is equal to total time taken divided by number of oscillation so for example a pendulum oscillates 10 times so the number of oscillation is 10 and it takes a Time of 5 Seconds so we have time and number of oscillation what is the time period so we have the formula time period is the total time taken divided by number of oscillation here the total time taken is 5 Seconds divided by number of oscillation there are work 10 oscillations so divided by 10 so you will get 0.5 seconds so that is the time period or time taken for the Bob to complete one oscillation topic number four is scalar and vector quantity so you should know how we represent the value of a physical quantity for example temperature so we will write temperature that is the physical quantity which is 40 degree celsius so here basically it consists of the physical quantity then a value the value is known as magnitude it will have a number that is magnitude then degree celsius as you can see which is the unit so basically this is how we represent any physical quantities where we will have the physical quantity the magnitude or the value which we represented in a number with a unit so another example I am showing here that is force we can write the force acting on an object is 100 Newton but we should mention the direction here if it is towards right the object will move towards right but if it is towards left object will move towards left so we can write down force is 100 Newton towards right here again we can see we have this part is physical quantity and 100 Newton where 100 is magnitude then it mentioned the direction also we have to mention the direction that towards right or left so when we look at these two examples we can see that in the temperature this is a physical quantity when we represent the temperature we don't have to mention about the direction Direction doesn't matter we can measure the temperature of a glass of hot water in any direction it will remain same but for force it we have to mention the direction because when the direction changes the object will move in different directions so Force when we represent it required not only magnitude but a direction such physical quantities which has both magnitude and direction is known as Vector quantities but when you look at the temperature we can see here we just need a magnitude we do not have to mention the direction such physical quantities are known as scalar quantities so here we can see physical quantities are of two types either scalar or vector so we have already seen scalar quantities are the quantities they have which have only magnitude is just a number no need to mention the direction but Vector quantities are the quantities which have both magnitude and Direction now you need to study some examples for scalars and Vector quantities if you think which physical quantity is required both magnitude and Direction you can easily get that are the examples of vector quantities so first we can start with scalar quantities the examples are speed time mass energy and temperature these are the examples given in the syllabus you show you how to memorize examples of vector quantities are Force weight velocity acceleration momentum electric field strength and gravitational field strengths again these examples are given in your syllabus so you have to memorize next topic is finding the resultant of two vectors by calculation or graphically and here you just need to find only how to find the resultant of two vectors they are at right angles so here for example two forces are acting on an object the of first force is horizontal uh which is say 30 Newton Force as you can see it is acting towards the right and the second force acting on the same object is a 20 Newton Force which is acting vertically downwards so when these two forces are acting on the object what will be the resultant motion of the object so we have to find the resultant of these two vectors there are two methods first method is by calculation where you can you will get a right angle triangle so you can use Pythagoras Theorem first you have to rearrange this redraw these two vectors using head tail method that redraw the horizontal Vector in the same direction as shown in the figure in calculation method you don't have to check the length exact measurements you just need to draw a rough diagram so by calculation method we can first we can draw the 13 Newton I'm I will this is the question which has given in the question two different vectors will be given they are acting at two directions so first step we have to redraw this one that first I am going to redraw the 30 Newton Force which is acting towards right you don't have to take the exact measurements only you should follow the direction so you can see that is horizontally towards right then I have to draw the second Vector that is 20 Newton I can see the 20 Newton force is acting downwards so I should connect this one as a head tail method I should connect the second Force to the head the tail of the second floor should connect the head of the first force or the head of the second Force I should connect to the tail of the first force in such a way I should connect so I have two options I can connect here so you can see head then tails are touching or I should draw here again head and tail are stretching I should not draw here because tile and tile are touching that is not a proper way or I cannot touch in this way I cannot draw where head then head are touching that is also wrong when you redraw the head and tail should connect so this is one correct method now we have redrawn these two vectors in such a way the head is touching the tile of the other one and we have followed the exact Direction 30 newton is acting horizontally towards right 20 Newton is acting vertically towards downwards okay now the resultant is nothing but the third side and the direction of the resultant where head is here so head should touch the head of the resultant you can see tail easier so the tail of the resultant should touch the tail of the other vector now what is the value of this result 10 here we can see this is a right angle triangle and the resultant here is nothing but the hypotenuse so we can use Pythagoras Theorem so hypotenuse is base Square plus height square that will be hypotenuse Square so the hypotenuse value will be square root of 30 square plus 20 square so we will get 36 degree sorry 36 Newton so that is the resultant of these two forces 30 Newton and 20 Newton the resultant is 36 but we need to calculate the angle so this angle if you need to find out this angle that is a angle between the horizontal and the resultant in that case this is angle that we can represent Theta you are you can use socato so you can use tan tan Theta is equal to opposite over adjacent where tan Theta is equal to opposite is 20 divided by adjacent is 30 Newton so Theta will be tan inverse of 20 divided by 30. so you will get the angle also so by calculation method you will get an accurate answer where you have to find the magnitude of the resultant using Pythagoras Theorem and you should find the angle using soccer toe that is the application of maths next one how to find the resultant for the same values using a scale drawing or graphically where you should take a ruler pencil and a protractor and you should rewrote this with exact measurements and Direction so first of all you can read row 13 Newton but we know that we cannot draw a 30 centimeter line in order to represent a 30 Newton or 20 centimeter line in order to represent a 20 Newton because we don't have that much space on your paper so what we have to do is you have to decide a scale very important one Mark most probably you will get for deciding the scale so the scale here we can take um 10 Newton is equal to 2 centimeter so what will be the values in order to represent 13 Newton we should draw a six centimeter line and in order to represent a 20 Newton we should draw a 4 centimeter line so we should write this ID proper scale and you should write it it's very important now you can take a ruler and draw this lines that is in order to represent 13 Newton you should draw a six centimeter line in the exactly in the given Direction so 30 Newton that means draw a six centimeter line which represent 30 Newton and that should be exactly towards right then you can draw the other Vector that is 20 Newton for 20 Newton we should draw a 4 centimeter line which should be downwards and it should be exactly at 90 degree so take a protractor and make sure the angle is 90 degree vertically downwards draw a four centimeter line that represents 20 Newton then using the ruler connect the third side then measure the length of the resultant and we will get 7.2 centimeter so we can convert back using our scale that sent two centimeter is 10 Newton therefore 7.2 centimeter will be is equal to uh 36 Newton so that is the resultant and we need to find out the angle so this is the magnitude of the resultant 36 Newton an angle from the horizontal line is this angle that you can keep a protractor and measure the angle and measure this angle Theta using a protractor so in the question if they have asked you to draw graphically or using scale method you should draw this way or using calculation you don't have to draw but you can use the Pythagoras Theorem if both options are given in the question always use calculation method because it takes less time and you will get a accurate answer