This is a quick video on how to draw a motion map, which like the title implies is a way of
representing motion. There are very specific rules to drawing one that we're going to go
over. The first step in drawing a motion map is to decide on a zero point and then draw an
arrow to represent the positive direction. Both of these are entirely arbitrary. You can choose any
point you want to be the zero point in general, that's just a common point where we measure other
positions from. So if you're two meters in the positive direction away from the zero point,
we would say you're at a position of positive 2 meters. Totally arbitrary. So you get to decide
where that is on the motion map. It's going to look something like this. We're going to draw a
point and say that this is the zero point and then draw an arrow coming out of it and indicate that
that is the positive direction, so if an object is moving in the opposite direction of the arrow,
it's moving in the negative direction. So I can now give you an example of drawing a motion map
itself. What a motion map does is it puts dots at the position that an object is at after different
amounts of time have passed. Usually there's one dot for every second of time. So for example,
if we had a car starting at the zero point here and the car started to move, I would put a point
where the car is for every second that the car had traveled like this. So I'm going to put a point
where it starts, and then as it moves forward I'm going to add a point for every second that
it's traveled. So we don't actually represent the physical car on the motion map. This is what your
motion map is going to look like when you actually draw it. No matter what object you're drawing,
you're just going to draw points representing its position at different amounts of time. And you can
see that the exact position is kind of arbitrary. Motion maps aren't always used very specifically.
Sometimes it's just a general picture of what an object is doing. The next thing to do is to
label these points with the time that it was when we drew them, so this is what that would
look like. Before time had started that was the first point and then time is equal to 1 second,
2 seconds, 3 seconds, 4 seconds, so the dots show where the object was after each second passed. The
next thing to do is draw arrows connecting each dot from where the object started to where it
stopped. The reason why we draw these arrows is because the arrows show the size of the velocity,
because velocity is displacement divided by time, and time is just 1 second for each dot,
an arrow that shows the length of each interval also shows the size of the velocity. So if there's
a larger distance between two dots that means that in that one second you are going faster because
the same amount of time passed, but you crossed a larger distance, so the arrows are a useful way of
representing how fast you are going on the motion map. So fast objects cover more distance in the
same amount of time and their velocity vectors are larger, so we can compare a faster car and
a slower car like this, and you can see that if I draw a dot for every one second that passes the
faster car has larger errors than the slower car, because the slower car was covering less distance,
so the dots are going to be closer together. If an object is standing still, like if we have a cow
sitting here and it's just standing still, we just draw the same dot every second, and we're just
going to put that dot above the previous dot like this just so we don't keep drawing in the same
place over and over again. So if you have dots that are kind of piling on each other like this,
what this means is that the object is standing still in one specific spot. To show an object
moving in the negative direction, we just have it move in the opposite direction of your positive
direction. So this is an example of the car moving in the negative direction, and you could also draw
arrows pointing to the left to connect those dots. We draw a double arrow above the first arrow to
show the acceleration of the object. These arrows show how much the velocity increases or decreases
in one second: the definition of acceleration. With every second the velocity arrow will get
one acceleration arrow line larger or smaller, so I'll show you an example. Let's say that at
time equals zero there's no velocity, but there is an acceleration arrow, so this acceleration arrow
is showing you how much faster you'll be going after one second. So it's going to show you the
increase in the velocity arrow in one second. So after one second the velocity is going to be the
acceleration arrow plus 0 because there's no velocity to start off here, so it's just the
acceleration arrow's length. And then after 2 seconds the velocity arrow is going to be the
acceleration arrow bigger than it was before like this, so the acceleration arrow is showing you how
much the velocity arrow is growing over time. So we can do that again. We're assuming that the
acceleration is just staying constant here, which it always does. It's very rare to get a changing
acceleration, so we connect that arrow and see that it's getting bigger and bigger and bigger. So you
can see that we can use these acceleration arrows to show you how much faster the object is getting
per second. If the acceleration arrow is pointing in the opposite direction of the velocity, like I'm
imagining that this is starting with a very large positive velocity. If it's pointing in the opposite
direction that means that the acceleration is actually slowing the object down. It's getting
slower over time. So if I combine the acceleration arrow with the velocity arrow like this, you can
see that it's pushing back against it, and so the new velocity will be smaller than before.
And it keeps pushing back against it, so it becomes smaller and smaller and smaller. So acceleration
arrows pointing in the opposite direction show you how the velocity is getting smaller over
time by that exact amount. And that's everything that you have to know about drawing a motion map.