1. What is the meaning of Velocity? PHYS 102 D Physical Science
Objects in Motion
What is the meaning of Velocity?
Zdeslav Hrepic
Fort Hays State University
PHYS 102 D Physical Science
Supported by NSF

2. Objectives
You will partially get involved and partially see demonstration of an activity-based method of teaching:
How to interpret distance-time diagram
The difference between:
Instantaneous and average speed
Speed and velocity
Instantaneous and average velocity

3. Goals At the end of the activity you will be able to:
Immediately utilize this method by using ready inquiry-based materials, Excel spreadsheets, digital camera and PowerPoint Animations.
Become familiar with further options with video editing by using Pinacle Studio program

4. Material
Originally developed through an NSF grant as teacher enhancement material (OPPS), later GRASPS
In revision by FHSU to be used as course material
Topics covered in modules divided in 5 step learning cycles
Today’s cycle: What is the meaning of Velocity
Word files

5. Average vs. Instantaneous speed
Average speed is the distance traveled divided by the time to travel.
Instantaneous speed is the average speed for infinitely small distances and times.

6. 5. Graphing speed: Configuration
Slow walker: Walk slow and steady.
Fast walker: Walk briskly but steady.
Fast starter: (Starts fast and than slows down): Run in a full sprint at the beginning. Be fast around 15m and then slow it down during the last 15m (second half of the trip).
Fast finisher: (Starts slow and than speeds up): Begin with a walk, jog somewhere around 15 m and run in a full sprint by 25m.

7. Practical tips Begin before start Finish after the finish line
Familiarize yourself with your stopwatch
Fast starter: and Fast finisher: Try to achieve big difference, steady change

8. Spring 2005 Data
Video 2

9. Matching Velocities – Clean data

10. Which v-t Graph Corresponds to the Given d-t Graph?

11. Which v-t Graph Corresponds to the Given d-t Graph?

12. Which v-t Graph Corresponds to the Given d-t Graph?

13. Which v-t Graph Corresponds to the Given d-t Graph?

14. What about the direction?
Activity:
Inquire 7

15. What about the direction?
Airplanes …
Speed is how fast is something going.
Speed = distance crossed / time elapsed
Velocity is the speed and direction of an object.
Velocity is a vector (has magnitude and direction).
Speed is a scalar (has magnitude only)

16. Speed and Velocity
Moving all the time equally fast (with respect to the ground) - called?
Constant speed
Moving all the time equally fast and also in the same direction?
Constant velocity
Do we always move equally fast?
Do we always move in the same direction?

17. Average and Instantaneous Speed Trip from home to college
Things to Consider:
Stop signs
Traffic lights
Speeds allowed
What does the car speedometer measure?
What is the police concerned about?

18. Average and Instantaneous Speed
Things to Consider for the each trip:
Average speed?
Maximum speed?
Time
What is the trip choice based on?
Unit conversion
2.8 mil in 5 min
1.8 mil in 6 min
Video 1

19. Average Velocity Things to Consider: Average Velocity?
Distance and Displacement
Average Velocity?
Avg. Velocity same or different for both trips?
Avg. Velocity after returning home
2.8 mil in 5 min
Straight Shot 1 mile
1.8 mil in 6 min

20. Average and Instantaneous Velocity
Things to Consider:
Average Velocity and Instantaneous Velocity
2.8 mil in 5 min
Straight Shot 1 mile
1.8 mil in 6 min

21. Reminder (Previous cycle): Distance and Displacement
START
FINISH
Need to distinguish how long we traveled from how far away (and in what direction) we traveled.

22. Distance and displacement
Distance and displacement are two quantities which may seem to mean the same thing, yet have distinctly different definitions and meanings.
Distance is a scalar quantity (has magnitude only) which refers to "how much ground an object has covered" during its motion.
Displacement is a vector quantity (has magnitude and direction) which refers to "how far out of place an object is"; it is the object's change in position.

23. Direction of the Average Velocity
START
FINISH

24. Direction of the Average Velocity
Displacement is a vector - Distance is not
Velocity is a vector - Speed is not
START
FINISH

25. Make sense: Velocity and speed
How would you determine the average speed of an object on these paths:
START
FINISH
START
FINISH
Average speed vs. Average velocity

26. Velocity is a vector Velocity is a vector
Vectors are quantities that have magnitude and direction
Speed is the magnitude of a velocity.

27. Average vs. Instantaneous Velocity

29. More Information / Feedback (
Thank You!