Physics is about energy and motion. A lot of what makes physics hard in higher level classes is the fact that motion occurs in 3 dimension of space (up/down, left/right and forward/backward).
Analyzing three-dimensional motion (or 2 dimensional motion) can be technical but does not bring very many new concepts.
In this class , we will almost always describe motion in one dimension. When we discuss motion in more than one dimension, it will always be qualitative.
Imagine we live in a Universe that is a single line. You can only move right/left (or up/down say).
We can denote our position on this line using a label
Let us look at the rocket motion in the video below done by Dr. Louis Leblond. This is a motion of a rocket-car in a straight line. The rocket started from rest and kept moving faster and faster each time from left to right.
To represent this motion, first imagine that the rocket and me are represented by a single point (imagine that we have no size). We can then do a series of snapshots of where the rocket car is at equal intervals of time (every second, for example).
This figure is very informative. It tells us the position of the rocket car at different instant of time. Since the interval of times are equal we see that the rocket car traveled a bigger distance between time 4 and time 5 than it did between time 1 and time 2. The speed was greater toward the end than it was at the beginning. The rocket car was accelerating .
In science, we often like to use graphs to represent and visualize information. A graph is an abstract, conventional way of presenting scientific information to an audience. A common graph has two axes. For example, here is a positive versus time graph.
** Hint: When you see a graph for the first time, start by determining what the vertical and horizontal axis represent!
So, for example we could decide to do a position versus time graph for the rocket car. To do that, we put points on the graph where vertical heights represent position and horizontal distance represents time. To help me do this correctly, I can rotate the rocket car left/right time-lapse image line (above) from horizontal to vertical. Then I separate each point at equal horizontal spacing for each time. This gives the following graph.
We can connect the dots by a line that goes thru all of them. The end result is
Note that the shape of the graph has nothing to do with what the actual motion looked like. The motion was on a line, the graph is in 2 dimensions. The graph is a representation of the motion (position and time together).