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Vectors and Scalars

Added Oct 12, 2015 •

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what I want to do in this video is talk about the difference between vectors vectors and scalars and they might sound like very complicated ideas but we'll see over the course of the videos that they're actually very simple ideas so first I'll give you a little bit of a definition and then I'll give you a bunch of samples and examples will make things super clear hopefully they'll make things super clear that Vector is something that has a magnitude magnitude and or you could kind of do that as a size and it has a direction and and it has a Direction has a direction a scalar only has a magnitude or size and if that doesn't make sense to you it will hopefully make sense to you in a second can I show you an example for example let's say that I have a let's say that that's the ground right there only do the ground in a more appropriate ground like so this is green right over here and let's say that I pick and I have a brick here I have a brick on the ground and I pick up that brick and I move it and I move it over to this place right over here so I move the right over there and then I take a ruler out and I say wow I moved the brick I have moved the brick five meters moved the brick five meters is my measurement of 5 is it a vector or scalar play just tell you five meters you just know the size of the movement do you just know the magnitude of the movement so if someone were to just say 5 meters 5 meters this is a scalar quantity  scalar quantity and when referring to moving something or how much something has I guess changed its position and I don't give you the direction we're talking about distance and I'm assuming you heard the word distance how far of a distance something traveled so this is distance so we could say that this block or this brick because of my picking it up and moving it has moved a distance of meters but if I didn't show you this picture here and someone just told you that it moved a distance of 5 meters you would know if it moved to the right five meters you would know if it move to the left 5 m up or down or in or out directions know it moved if you want to specify that so we could say that this brick right over year that it moved 5 5 m to the 5 m to the left to five meters to the left now we have specified a magnitude right over there so that is a magnitude and we have specified a direction to the left now explicitly known they went 5m to the sorry it should be readers to the right let me change that so five meters to the to the that's why the direction to the right is what it got move fire started here it went 5 meters to the right so once again the magnitude is 5 meters and in the direction is the right so what I've just described to you right here is a vector quantity so this all of this business right over here this is a vector and when you talk the movement the change in position and you gave us Direction the vector version of distance I guess you could call it is displacement so this right here is displacement displacement so the correct thing to say you would say that this brick has been displaced 5m is to the right or it has been moved a distance of 5 meters distance is a scalar quantity I didn't tell you one direction placement is a vector quantity we told you that it is to the right I must explore this if we talk about the actual will talk the speed or velocity of something so let's say that my let's say that my that this 5 meters was traveled and let's say that the change in let's say that the change in time and when I let me just cuz you're probably not familiar with that mean so let's say that the change in time right here change in time when I moved this block 5 meters let's say that it was I don't know it say that the change in time was to so maybe right when I when the block started moving maybe on my stopwatch it said 0 and then on my stopwatch when it stopped moving its open it got to this position I should say when it left from this position my stopwatch said zero when it got to this position my stopwatch said 2 seconds so the change in time or the we're dealing with is two seconds and this is you know for all we know time only goes in the positive direction so you can you consume that it's what you could you could pick that as a vector or scalar I guess cuz there's only one direction for time the simple physics so what's a measure of how fast this thing moved so how fast did this thing move so we could say it moved 5 m in two seconds let me write this down so it moved 5m it moved 5m per 2 seconds her two seconds or we could write this as 5/2 of a meter per second or 5 played by 2 is what 5/2 is 2.5 meters per second meters second meters per second this right here is just the 5/2 let me make that clear that right there is just the 5 / the two so my question to you this 2.5 meters per second tells you how how far it traveled in a certain amount of time is this is vector or scalar quantity just ate a size of how fast it went or is it also giving direction why don't you any direction here so this is a scalar quantity and the scalar quantity for how fast something is going for how fast something is going is speed we can say that the speed of the brick is 2.5 meters per second now if we do the same calculation we say it went to if we say it went 5 meters 5 I'll just write M 4 meters 5m to the right in two seconds in two seconds then what are we get we get 2.5 once again 2.5 meters per second abbreviate them as meters per second meters per second to the right to the right so is this a vector or scalar quantity I'm telling you the the the magnitude of the speed that's right here this is the magnitude 2.5 meters per second and I'm also telling you the direction to the right so this is a vector quantity this is a vector quantity and when you specify speed and the directions of the 2.5 meters per second is a skater and the direction you are talking about velocity you are talking about velocity so easy way to think about it if you're thinking about changing position and you specify the direction of the change in position you're talking about displacement not talking about the direction you want the scalar version you're talking about distance if you're talking about how fast something is going and you give the direction that it's going in your talk about velocity if you don't give the direction you are talking about speed hopefully that that helps you a little bit in the next video going to start working with these a little bit solving some basic basic questions about how fast something is going on how far it might travel or how long it might take it to get some please

Uploaded by James Dorman.

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