in this video we'll be talking about the average speed and the average velocity the average speed is defined as the total distance the total distance the total distance divided by the total time but so that's how the average speed is defined the unit of the average speed is the meter per second because the unit of distance is meter and the unit at time is second the average speed is again always positive it cannot be negative because the distance is a scalar quantity it has only magnitude it does not have direction so the average speed is again a scalar quantity that means it does not have any direction it has only magnitude now let's talk about the average velocity the average velocity the average velocity is ditch is the total displacement divided by the time how much displacement an object has traveled in a given time is the displacement look at the notation here here the average velocity is defined by the denoted by V and there is a sign here and the bar sign here this sign this one represents the average velocity they so if anything that does have a little hat over admin's it is the average alright mathematically the mathematically evidence velocity is given by the change in the the position divided by the change in the time or the change in the position is given by the final position one initial position / the final time - elk initial time the TF is the final time and this is the initial time all right this is a vector quantity the displacement is a vector quantity that means it has both magnitude and it has direction again the unit is meter per second so here we talked about the average speed and the average velocity now now let's take a difference between both and we'll go through the the differences by given an example so let's start from this point in this one so here you have a particle or an object which is started from point a and it is moving in a rectangle and the and the direction is given by this way it is moving from point a in a in a rectangle this way and come back to exactly the same position now you need to find out what is the average speed and what is the average velocity so look at the definition here what is the average speed here the air is a speed is the total distance divided by the total time so we have to calculate what is the total the distance so the total distance is the total path which is 4 meter 3 meter 7 4 meter plus 3 meter so the distance divided by the time and what is the total distance this 4 meter plus 3 meter 4 meter plus 3 meter so it is 4 plus 3 plus 4 plus 3 and the total time is given which is 7 second so it will be the total will be 14 divided by 2 which is again sorry 14 divided by 7 which is 2 second the 2 meter per second that is the average speed now let's calculate the average velocity the average velocity is a final position minus initial position or the displacement divided by time by the time so what is the displacement the displacement is the length connecting initial and the final point if he connect the initial and the final point it is exactly zero so they are in other words there is no change in the position the object or the portion or the man came back to exactly the same position after moving in a complete rectangle so there is no change in the position or the initial position and the final position is exactly the same so there is no change in the position that means the total displacement is zero the time is seven second if we divide it you again get the giro meter per second so you see the average speed is two meter per second but the average velocity is a jido meter per second so what does the era's velocity gives you the heaviness of velocity tells you what is the the position after a certain time so as the position is exactly the same so the object did not move any of the change in the position of the object is exactly the same all right so that is the average the difference between the average speed and the average velocity now let me give you another example here again you have the two persons here the one person is started moving to the right this way and the another person started moving to the left both person has moved were a 5 meter in exactly 2 seconds now let's calculate the average speed and average velocity for both objects average speed to the average reader every dispute and this is for person 1 and person to the earliest speed is denoted by s s bar or as we simply call this bar here so what did ever is a speed of the person 1 the distance divided by the time the distance is 5 meter and the time is 2 so it will be 2 point 5 meter per second and again for the person to in the distance the distance is 5 meter divided by the time it is a steal 2 point 5 meter per second so that every the speed or both is exactly the same now let's calculate the average displacement sorry average velocity the average velocity is denoted by V a line on the top or equal V Bar the fourth partial one I'm here denoted by s a and or s1 or s2 just to make a differences be one for the person 1 but the person 1 what is the displacement the displacement is 5 meter we call this tool seen as a positive relation so this is the 5 meter divided by the time 2 and this 1 will be negative positive 2 point 5 meter per second and 4% to the average velocity is the displacement now what is the displacement in this case for the person - for the person to the displacement is negative five meter and the reason is it has moved in the opposite direction and the time is exactly the same so it will be negative two and a half meter per second so that is the average velocity for person one and this is the average velocity for the person - you see the difference here the one is positive and the other is negative while the average velocity for both object or so whatever is a speed for both person is exactly the same but the average velocity the magnitude is the same but the direction is opposite now let's take another example here so let's say you started moving from this point a along this line here and then this is your final position now we have to calculate what is the final or what is the average speed and what is the average velocity so again every is a speed how do you define the average speed the average speed is defined as the the change or the total distance divided by the time what is the total in the distance the total distance is 3 meter plus the 4 meter here this three meter plus four meter and the total time the total time is two second plus three second so 7 divided by 5 and the 7 divided by 5 is 1 point 4 1 point 4 meter per second and this is the average speed now how to calculate the average velocity in this case the evidence velocity is defined as the the displacement and how do you calculate the displacement the length of this path a straight line connecting initial and the final point it gives you the total displacement and what is the length connecting point a and point B this is given by a square root of 3 squared plus 4 squared so the average velocity is now 3 squared plus 5 squared this will be 5 meter 5 meter so in this case the displacement divided by the time so the displacement in this case is 5 meter and the time is 2 the total time is again 5 second to a second and this is a 3 seconds so the total time is 5 seconds so the area's velocity is 1 meter per second and the average speed is 1 point 4 meter per second as I mentioned the velocity is a vector quantity it has both magnitude and direction this gives the magnitude now what is the direction how do you find out the angle in order to find out the angle this is the angle now we can calculate this angle if you look at this in triangle here this triangle this sign theta from this triangle is P which is 4 over H and this is the H here 5 so if we do the math 4/5 sip sign you'll get theta with 53.1 3 the degree so that gives you d the angle so this is the magnitude and this is the angle that means the person travels from point A at an angle of fifty three point one three degree at Alice and the nine stood of the velocity is one meter for second and and this is the direction so this is the magnitude and this gives you this the direction alright thank you