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So we have some, some race cars 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 turn
at a constant speed.
So a constant speed
constant speed of 100 kilometers per hour.
100 kilometers per hour.
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 look at this speedometer for the car here,
If I look at this speedometer over here
it won't budge, it just stays in a 100 kilometers 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 why would Sal
even make this video, you know,
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
having speed with a direction
having a magnitude and a direction.
And to think about.
Let's take a top view of this thing
And I think It will become a little bit clearer
the difference between speed and velocity
and why these things are accelerating.
So, if I were to take a top view of this race track.
I'll do my best attempt to draw it.
So, it might look something like this.
This is the top view.
I can even draw this red and white.
So, red, just to give you the idea.
So, this is the red
and there is some white in between.
I miss 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.
And there's some grass out here,
there's some grass over here,
and there is some grass over here.
And let's focus on this orange car,
this red car over here.
So, (where?) you say..
And this is a top view.
This is it's path right over here.
(We're?) saying it has a constant speed
of a 100 kilometers 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 100 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, where it's 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 draw
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 arrow
will always be constant, but as we see
it's direction changes, when it's halfway through the turn
it's not going in the same direction.
It is now going in the different direction,
and when it comes to the bottom of the turn
it's going in the very different direction.
And it'll keep, the direction keeps changing
as long as it is turning.
And I'm not gonna go into math here, we're gonna 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 change,
over a change in time.
And although the velocity's magnitude is constant here
its direction is changing
it keeps being...
if there's no acceleration on it
it's magnitude and the direction of it's 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 (...) this is kind of a little bit trick question,
something for you to think about,
we're gonna to discuss the math in more detail
in future videos.
But what's happening here is the,
the car is actually (are) accelerating.
And they're actually accelerating inwards,
and that's what's changing inwards.
We wanna say inwards.
They're being accalerated 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.