1. Velocity-Time(VT) Graphs
Mr. Fedell

2. VT vs. PT graphs
A position-time (PT) graph tells you where an object is. A velocity-time graph tells you how fast it’s moving. **(VT graphs DO NOT give in position info!)**

3. When an object stays still for 10s, its velocity is 0 m/s.

4. Constant Velocity
CV –AWAY CV-TOWARDS

5. Speeding up or Slowing down
Speed up – away Slow down – away Speed up – toward Slow down - toward

6. This may help…
AWAY STILL TOWARDS

7. V vs. T Graphs WS Practice!

8. V vs. T Graphs WS KEY!

9. PT and VT – Motion Detector Lab
File  Open  Additional Physics  Real Time physics  Mechanics  Open file “Constant Velocity”
Extend data collection from 5-10 seconds.
Capture the PT and VT for a JEEP backflip
Sketch well-labeled graphs. Label parts as CV-away, still, CV-towards
Obtain the slope of the PT on both the CV away and CV towards sections, compare with your VT graph! (show all work below)

10. This may help…
AWAY STILL TOWARDS

11. “Racing Questions” In this race, who is: Moving faster
i. at 0 seconds?
ii. at 5 seconds?
iii. at 10 seconds?
b) Moving with a positive velocity?
c) What does the intersection indicate?
d)Who started “ahead”?

12. Practice – Racing problems!

13. Converting from POSITION to VELOCITY Graphs
The slope of a P-T graph is the velocity.

14. Making a VT from a PT 0 m/s -10 m/s +20 m/s 0 m/s Velocity (m/s) +40
-30
-20
-10
-40
+10
+20
+30
+40
Velocity (m/s)
0 m/s
-10 m/s
+20 m/s
0 m/s

15. Practice - Page 3

16. Page 3 - KEY
See white board.

17. Velocity from Position – Motion Detector Lab
File  Open  Additional Physics  Real Time physics  Mechanics  Open file “Velocity from Position”
Sketch well-labeled PT and VT graphs
for CV-Away, Still, and CV-Towards

18. Concept Review What information can we gather from a PT?
What value does slope represent?
A negative slope indicates what?
What information can we gather from a VT?
Can we obtain position information from a VT?
What is indicated when an objects velocity goes from + to – ?
What value might slope represent? (units?)

19. More Practice!!!

20. SLOPES! The slope of PT graph gives the velocity (m/s).
The slope of a VT graph gives the acceleration (change in velocity)
Includes both SPEED UP and SLOW DOWN
Unit for acceleration = m/s2 or m/s/s

21. SLOPES! So what does an acceleration of 1 m/s2 mean?
How about 5 m/s2 ?
Kingda Ka: 11 m/s2 !!!

22. SLOPES! A slope of ZERO indicates CONSTANT VELOCITY or STILL…
Still CV-AWAY CV-Towards

23. SLOPES!
A steeper slope the higher the acceleration. It’s the more QUICKLY and object can CHANGE its VELOCITY.
Motorcycle Wheeler

24. For this velocity-time graph…+ -
Velocity (m/s)
Still CV
Speed up
Slow down
Changing velocity
Object is moving fastest
Moving away
Moving towards

25. For this velocity-time graph…
+80
- 80
Velocity (m/s)
+60
+40
+20
When does this object change direction!?
-20
-40
- 60

26. Graph Matching Lab
File  Open  EAS_SHARES Drive  Bauer  STU_SHARE 
Logger Pro Files  Graph Matching Folder
2. Your group’s job is to match graphs 1-3!

27. Practice Quiz Question #1
At rest
Constant velocity
Speeding up
Slowing down
Moving away from the origin
Moving towards the origin
Farthest distance from the origin

28. Practice Quiz Question #240 35
Initial position?
Final position?
Displacement?
Velocity at each stage? 30 25 20 15 10 5

29. Practice Quiz Question #3+8
- 8
Velocity (m/s)
At rest
Constant velocity
Speeding up
Slowing down
Moving away from the origin
Moving towards the origin
Farthest distance from the origin +6 +4 B A C +2 D G F E -2 -4
- 6

30. Draw the PT for the following scenario:
You walk to Java City for 5s
You slow down as you approach the line for 5s
You wait in line for 5s
You turn around and speed up for 5s
You walk at a constant velocity for 5s

31. Convert the PT from last slide to a VT

32. Sign of Velocity and Acceleration
If an object has zero acceleration, it is:
Still
CV-AWAY
CV-TOWARDS
Change in velocity (slope of a VT graph)

33. Acceleration has a direction
It’s not always pointing in the same direction you’re moving…
Scenario 1: Speeding up
(gas pedal)
+ Velocity
Scenario 2: Slowing Down (brakes)
+ Velocity
+ Acceleration
- Acceleration

34. Sign of Velocity and Acceleration
If you are accelerating in the SAME direction you’re moving…Speeding Up
Reverse Forward
 V (-) V (+) 
 a (-) a (+) 
If you are accelerating in the OPPOSITE direction you’re moving…Slowing Down
Reverse Forward
 V (-) V (+) 
 a (+) a (-) 