1. Constant & Changing Motion

2. Reference Point A fixed point from which direction is defined.
The reference point can be anything.

3. Distance The length traveled measured from start to finish.
Use meters!!!

4. Example #1
A car drives 4 meters north, 3 meters south, then 5 meters north. What’s its total distance driven?
D = 4m + 3m + 5m
D = 12m

5. Direction Represented by using : (+) or (-) signs Up or Down
Right or Left
Forward or Backward
North, South , East or West

6. Position
Where something is, relative to the reference point.

7. Displacement
The net difference between the starting point and the ending point.
Dd = dfinal – dinitial

8. These are the vectors that we’ve been practicing!
Example #2
A car drives 4 meters north, 3 meters south then 5 meters north. What’s its displacement?
Δd = 9m north – 3m south
Δd = 6m north
These are the vectors that we’ve been practicing!

9. Time Interval The difference between two clock readings
t = tfinal – tinitial
Use seconds!!!

10. Speed Total distance traveled divided by the total time elapsed.
speed = distance/time

11. Average Velocity ( Vavg)
Total distance traveled divided by the total time elapsed.
Vavg = Dd/Dt Units: m/s
Magnitude (size) and direction

12. Δt includes ALL time, whether you were moving or not!
Average Velocity
Δt includes ALL time, whether you were moving or not!
1 second
2 minutes
3 seconds
1 mile
2 miles
2 miles
home
Dairy
Queen
4 hr.
EXXON
3 hr.
LHS
5 miles
Δt = 1 sec sec sec sec + 3 sec
Δt = sec (x 1 hr / 3600 sec = 7.03 hr)
Vavg = 5 mi / 7.03 hr
Vavg = 0.71 mi/hr

13. What is the difference between speed and velocity?
Velocity is a vector quantity (magnitude & direction)
Speed represents the magnitude of velocity (scalar quantity)

14. Instantaneous Velocity (V)
Velocity at one point
Δd and Δt are very, very, very, very……small!

15. Constant Velocity
If a body is moving at a constant velocity, the velocity never changes between intervals.
Doesn’t happen often in real life!
Ex:
V = 10 m/s
V = 10 m/s
V = 10 m/s

16. Changing Velocity Here, the velocity changes between intervals. Ex:
V = 10 m/s
V = 15 m/s
V = 20 m/s

17. Acceleration Acceleration is the change in velocity over time.
Average acceleration (aavg ) = change in velocity
time spent
aavg = ΔV / Δt
Units: (m/s) m
s s2

18. Acceleration Example #1
Find aavg.
Δt = 2 sec
Vi = 10 m/s
Vf = 40 m/s
aavg = 40 – 10 m/s
2 s
aavg = 15 m/s2
*This means that the object’s velocity increases 15m/s every second!

19. Acceleration Example #2
Find aavg.
Δt = 2 sec
Vi = 40 m/s
Vf = 10 m/s
aavg = 10 – 40 m/s
2 s
aavg = -15 m/s2
*This means that the object’s velocity decreases 15m/s every second!

20. Acceleration Example #3
Find aavg.
Δt = 2 sec
Vi = 40 m/s
Vf = 40 m/s
aavg = 40 – 40 m/s
2 s
aavg = 0 m/s2
*This means that the object’s velocity is constant!

21. Four Basic Equations of Physics
Conditions:
One-dimensional motion
Constant acceleration

22. Four Basic Equations of Physics
Vf = Vi + at
d = Vi t + ½ at2
2ad = Vf2 – Vi2
Vf + Vi 2
d = t