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Current time:0:00Total duration:4:49

Video transcript

so we have some some racecars racing right here and I have an interesting question to ask you if we assume that these cars are making this turn right over here that all of them are making this term at a constant speed so a constant speed constant speed of 100 km/h 100 km/h my interesting question for you is are these cars accelerating while they make this turn so is acceleration happening acceleration and you might say well gee look my speed was constant it's not changing if I looked at the speedometer for the car here if I looked at the speedometer over here it won't budge it just stays at 100 kilometres per hour I don't have any change in speed over time and so then you might say that you don't have any acceleration but then you might be saying well why would Sally even make this video you know and why would that question even be interesting and your second your second suspicion would be true because these cars actually are accelerating they actually are accelerating despite having a constant speed and you can pause it and think about that for a second if you want to but I wanted to point this out to you because in an example like this the difference between speed and velocity starts to matter speed being a scalar quantity only having a magnitude and velocity being a vector quantity have being speed with a direction having a magnitude and a direction and to think about let's take a top view of this thing and then I think you'll become a little become a little bit clearer the difference between speed in the end velocity and why these things are accelerating so if I were to take a top view of this racetrack do my best attempt to draw it so it might look something like this this is the top view I could even draw this red and white so red just to give you the idea so this is the red and there's some white in between obviously I'm not drawing as many dividers as there are in the actual picture but it gives you an idea of what I'm actually drawing then there's some grass out here so there's some grass over here and then there's some grass over here and let's focus on this orange car this red car right over here so where you say and this is a top view so it's this is its path right over here and we're saying it has a constant speed of 100 kilometres per hour so if you think about its velocity if you think about its velocity the magnitude of its velocity is constant it is a hundred kilometers per hour but what is happening to the direction of the velocity remember velocity is a vector quantity it has magnitude and direction so up here at this one is starting to enter the curve it's going in this direction and you tend to show vectors by arrows like this and what you do is the arrow is going in the direction of the velocity in this case and normally you would draw the the length of the arrow shows what is the velocity the magnitude of the velocity I should say so its velocity is constant so the length of this hour will always be constant but as we see its direction changes when it's halfway through the turn it's not going in that same direction it is now going in a different direction and when it comes to the bottom of the turn it's going in a very different direction and it'll keep the direction keeps changing as long as it is turning and I'm not going to go into Matthew we're going to wait for the math on this a little bit later but remember acceleration is a change in velocity over time acceleration is equal to a change in velocity is equal to a change in velocity over time or we could say over a change over a change in time and although the velocities magnitude is constant here it's Direction is changing it keeps being it if it had no if there is no acceleration on it its magnitude and the direction of its velocity would be constant and the car would just keep going would just keep going in that direction so somehow the car is the car's direction is changing inward over and over and over again and so I this is just kind of a little bit of a trick question something for you to think about we're going to we're going to discuss the math in more detail in future videos but what's happening here the cars actually are accelerating and they're actually accelerating inwards and that's what's changing in words when I say in words they're being accelerated towards the center of the curve they're being accelerated to the center of the curve and that's what's allowing their direction to actually change