1. 8Th Grade Science Ms. McKinley
Graphing Motion
8Th Grade Science
Ms. McKinley

2. Why do we need to graph anyway?
VERY useful tools for summarizing info
show us how something changes over a period of time
organize data in a visual way
uuuh, what’s the point?
Purpose of graphing

3. X-axis and Y-axis must be labeled
Parts of a graph
X-axis and Y-axis must be labeled
you must write down what is on each axis.
Label of y-axis is TEMPERATURE
Label of x-axis is TIME

4. Shows how an object’s POSITION is changing over time
Position vs. Time graph
Shows how an object’s POSITION is changing over time
Shows how an object is moving (away or toward the reference point)
Purpose of graphing

5. Position vs. Time graph (contd.)
Each number has UNITS
Position has units of distance like cm, m, and km
Time has units like seconds, days, and years.

6. Video clip: Position vs. Time graph
Note: Position vs. Time graphs
are THE SAME as
Distance vs. Time graphs
Video clip: Position vs. Time graph

7. Slope of a Position vs. Time graph
The steepness of a line on a graph is called the SLOPE.
The steeper the slope, the faster the object is traveling.
On a position-time graph, a steeper line = greater average speed.
You’re going the wrong way!
PREGUNTA: In this position-time graph of two turtles racing, which turtle had the greater average speed, the RED one or the GREEN one?

8. Constant Speed on a P vs. T graph
A flat (not-curved) slanted line on a P vs. T graph shows that the object is moving at a CONSTANT SPEED.

9. Calculating the slope on a Position vs. Time graph
The SLOPE of a position vs. time graph is the AVERAGE SPEED RISE = change in vertical direction RUN = change in horizontal direction
rise
run
slope =

10. Let’s practice Calculate the average speed of Turtle 1.
Remember, the SLOPE of a position vs. time graph is the AVERAGE SPEED

11. Show how the SPEED of an object changes with time
Speed vs. Time graphs
Show how the SPEED of an object changes with time
CONSTANT SPEED on a speed-time graph is a horizontal line b/c the speed doesn’t change.

12. Speed vs. Time graphs (contd.)
If an object speeds up, the line slants UP toward the right

13. Speed vs. Time graphs (contd.)
If an object slows down, the line slants DOWN toward the right.

14. OK, now let’s try it out!