1. Lecture 2.3: Graphing Motion part 1
8Th Grade Science
Ms. McKinley

2. Why do we need to graph anyway?
VERY useful tool 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. Position vs. time graphs (same as Distance vs. Time Graphs
We will be learning about TWO types of graphs. The first is…
Position vs. time graphs (same as Distance vs. Time Graphs

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.)
UNITS
Position has units of distance like cm, m, and km
Time has units like seconds, minutes, and hours.

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

7. Slope of a Position vs. Time graph
SLOPE: the steepness of the line
The steeper the slope, the faster the object is traveling.
On a P vs. T 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. Calculating the slope on a Position vs. Time graph
The SLOPE of a P vs. T graph = the object’s AVERAGE SPEED
RISE = change in vertical direction
RUN = change in horizontal direction
rise
run
slope =

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

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

11. Lecture 2.4: Graphing Motion part 2
8Th Grade Science
Ms. McKinley

12. Last week we learned about…
Position vs. time graphs (same as Distance vs. Time Graphs)
Now we will be learning about….
SPEED vs. time graphs

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

14. Speed vs. Time graphs (contd.)
If an object SPEEDS UP, the line slants UP toward the right
The object’s speed is INCREASING.

15. Speed vs. Time graphs (contd.)
If an object slows down, the line slants DOWN toward the right.
The object’s speed is DECREASING.
Speed vs. Time graphs (contd.)

16. OK, now let’s try it out!