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Motion

So what's the point of all this review of line graphs and variables?

Well, line graphs have the ability to show different aspects of one-dimensional and two-dimensional motion, including:

• Displacement
• Velocity
• Acceleration
• Time

As you can see from the list, all of these are key variables when it comes to motion.

The next lesson will look in much more detail at these graphs. However a couple of key things to be aware of regarding motion graphs are:

• Time is usually placed on the x-axis since it is most often the independent variable in motion (remember, time is normally in seconds!)


• The dependent variable is placed on the y-axis; the dependent variable is usually one of the remaining three variables we mentioned above:
  • displacement,
  • velocity, or
  • acceleration

Remember the graph above from the previous lesson on free falling objects? It is a great example of a motion graph. Notice the following:

• The variable “time” (measured in seconds) has been placed on the x-axis.
• The variable “velocity” (measure in m/s) has been placed on the y-axis.

Let's see if you remember what this graph is showing.

What does this graph show about the velocity of the object?

Is the velocity increasing, decreasing, or staying the same as time passes?

Answer: The velocity is increasing as time passes! You can see on the graph that every second shows velocity increasing by 10 m/s. So at 1 s the velocity is 10 m/s and at 2 s the velocity is 20 m/s.

The next lesson will examine these types of motion graphs in much greater detail.