1. Speed and Velocity

2. What is Speed? How would you define speed?
A measure of the distance an object travels per unit of time
What do you think the formula for speed is – knowing the definition?

3. Units of Speed

4. Increase Decrease Speeding Up!
So, knowing the formula for speed, what would we need to do for distance and what for time to speed up?
Increase
Decrease

5. Constant Speed vs. Changing Speed

6. Constant Speed
The rate of change of position in which the same distance is traveled each second

7. Instantaneous Speed
If the speed of an object is changing, it might be helpful to know the object’s speed at a specific moment
Instantaneous speed- speed at a specific instant in time

8. Think!
How would the distance the car travels each second change if it were slowing down?

9. Average Speed
The total distance traveled divided by the total time taken to travel that distance

10. Math You Can Do! d = 360m T = 4s What is your average speed?
Average Speed = 360m/4s
90 m/s

11. Guess What?
Average speed is actually velocity! You already know velocity!

12. Vocabulary So Far Speed Constant Speed Instantaneous Speed
Average Speed

13. Practice!

14. Remember you have a test September 3rd!
Graphing Speed
Remember you have a test September 3rd!
Be sure to check the website for information as well as the calendar at the bottom of your class’s page!

15. What is the Formula for Speed One More Time?

16. So When We Graph Speed… It is a distance-time graph!
Graphs that compare the distance an object travels to the time it takes to reach its destination
X Axis = Time
Y Axis = Distance

17. Distance
Time 5 10 15 20 25 30 35 40 50 60 70

18. Comparing Speeds
When horse A reached the finish line, horse B was only 1.5 km from the starting point of the race
Horse A traveled a greater distance than horse B in the same amount of time.
Horse A had a greater average speed.
Measure the slope of the line to determine speed

19. They are moving at a constant speed!
Work With Your Table
What is the instantaneous speed at 40 seconds for horse A and for horse B (You can leave it as a fraction)
A = .75/60 = km/s
B = .75/ km/s
2) Both horses have show a straight line. What does this show about their speed?
They are moving at a constant speed!

20. Get a Textbook and Your Science Lab Book
SILENTLY read “using a distance-time graph to calculate speed” and “distance-time graph and changing speed” on pages 21 & 22
I HIGHLY suggest you take notes as you read
Don’t do anything with your lab notebook right now

21. Let’s Do Some Examples Constant speed Speeding up Slowing down
Stopping

22. Working with the Person NEXT to You
Create a distance-time graph example of a constant speed of your own. Calculate the speed of your object by finding the slope of the line.
What is the average speed?
Create a distance-time graph example for each scenario below. Find the speed for three points along the graph (A, B, C). Then find the average speed of points A, B, and C)
Slowing down
Stopping
Speeding up

23. Would You Like to Move Your Test to Thursday September 4th ?
Velocity
Would You Like to Move Your Test to Thursday September 4th ?

24. Velocity WITH DIRECTION Both the speed and direction of an object
Speed: A car travels 60km/h
Velocity A car travels 60km/h to the north
WITH DIRECTION

25. Representing Velocity
The velocity of an object can be represented by an arrow
The length of the arrow indicates speed
A greater speed is shown by a longer arrow

26. Why are the arrows the same length?

27. Constant Velocity
Remember constant speed? Well this is the same thing but with velocity (a direction)
Well if there is a direction, and it’s constant, then there has to be a constant direction!

28. How can velocity change?
We can change the speed or the direction

29. Changing Velocity
If either the speed or the direction changes (or both) then the velocity changes
A car on a curved track may have a constant speed but, because its direction is changing, its velocity is not constant.
We will see in the next section that it is accelerating

30. Changing Velocity Changing Speed and Direction

31. So How is Velocity Different From Speed?