1. Describing Motion
The graphs…
Game

2. To begin, consider a car moving with a constant, rightward (+) velocity of 10 m/s
What would a Position vs Time graph of this motion, look like?

3. Now consider a car moving with a changing, rightward
(+) velocity that is, a car that is moving rightward and speeding up or accelerating.                                                                    
And the graph’s shape is?

4. The slope of the line on a position-time graph is the velocity of the object.

5. And the slope is…

6. = 0.5 m/s Same for A and B = 0.5 m/s a = 0 m/s2
Example A car moves in a straight line and its odometer readings are plotted against time.
a. Find the speed of the car at points A and B.
= 0.5 m/s B
Same for A and B A
b. What is the car's average speed?
= 0.5 m/s
c. What is its acceleration?
a = 0 m/s2

7. Let’s compare the motions shown here
Compare the velocity of the red line to the…
Green line
Blue line
Orange line
Black line
And this trip shows?

8. What if the shape of the graph is a curve?
A curve shows a changing velocity or acceleration.
Slope of a curve?
V1 = (23m -18m) = 10m/s
(3.5s -3.0 s)
(3.0s, 18m) and (3.5s, 23m)
V2= (9m - 6m) = 5 m/s
(2.0s - 1.4s)
(1.4s, 6m) and (2.0s, 9m)

9. What shows the instantaneous speed in the car?
The instantaneous velocity of an object at a certain time is the slope of the position (displacement) versus time graph at that time. It can be positive, negative, or zero.
What shows the instantaneous speed in the car?

10. Describing Motion The graphs… Homework: Graphing Motion #1
NOT!! Be ready next class for
2 wkshts instead of one.

11. The Sonic Ranger Lab
In this lab you will measure your motion with a sonic motion detector. The motion detector emits sound waves and then detects them after they have reflected off of some object (such as you or your lab partners!). A computer then records distance from the detector to the object as a function of time. You will practice making and interpreting position-time graphs.