1. Speed & Velocity
Chapter 5.2

2. Let’s talk speed!!!

3. What is the difference between speed and velocity?
scalar
A one-component quantity having no direction
MAGNITUDE ONLY

4. What is the difference between speed and velocity?
scalar
Examples: time 10 min volume 10 gal weight 10 lBs
MAGNITUDE
ONLY

5. What is the difference between speed and velocity?
a scalar
the ratio of distance to time traveled.

6. What is the difference between speed and velocity?
10 meters/second or 10 m/s An object travels 10 meters in one second

7. Manipulating Speed Units
speed x time = distance
10 m x 10 s = 100 m s

8. Manipulating Speed Units
distance = time
speed
10 m = 2 s
5 m/s

9. instantaneous Speed speed measured at a particular instant.

10. instantaneous Speed
You’re traveling down I-95 at a constant speed of 75 mph.
What is your instantaneous speed?
Your instantaneous speed is the speed at any “moment”
in time. Since you’re traveling at a constant speed of
75 mph, your instantaneous speed is 75 mph.

11. Average Speed speed computed for the entire duration of a trip
Average speed = Total distance Total Time
v = dx/t
Average Speed

12. Average Speed Average Speed You travel to Atlanta per the following:
3 hours for 220 miles
4 hours for 280 miles
1 hour for 80 miles
What is your average speed?

13. Average Speed Average Speed You travel to Atlanta per the following:
3 hours for 220 miles
4 hours for 280 miles
1 hour for 80 miles
Vavg = = = mi hr

14. What is the difference between speed and velocity?
Two-component quantity having
magnitude & direction
Vector

15. What is the difference between speed and velocity?
examples:
10 m/s South
40 mph upward
Vector

16. What is the difference between speed and velocity?
a vector of the ratio of distance to time traveled.
velocity

17. What is the difference between speed and velocity?
scalar
50 m/s
vector
50 m/s South
speed
velocity

18. Combining Velocities Vectors are represented by arrows …
Length of arrow equates to quantity
of scalar represented
Point of arrow shows direction
50 km/hr East
20 km/hr West

19. Combining Velocities Vectors can be added (if in the same direction)…
10 m/s
15 m/s + =
5 m/s

20. Combining Velocities Vectors can be added (if in the same direction)…
Current
5 m/s
2 m/s
7 m/s

21. Combining Velocities Vectors can be subtracted
(if in opposite direction)…
10 m/s
5 m/s - =
5 m/s

22. Combining Velocities Vectors can be subtracted
(if in opposite direction)…
50 m/s
300 m/s
250 m/s

23. Combining Velocities Vectors can be subtracted
(if in opposite direction)…
50 m/s
300 m/s
Resultant
Velocity VR
250 m/s

24. Combining Velocities Vectors can be added (if in the same direction)…
Current
5 m/s
2 m/s
Resultant
Velocity VR
7 m/s

25. Combining Velocities Resultant Velocity The result of
combined velocities

26. Combining Velocities Vectors can be combined Right Triangle
5 km/hr
Right Triangle
Pythagorean Theorem
A2 + B2 = C2
= c2
= c2
169 = c2
13 = c
5 km/hr
12 km/hr
13 km/hr
12 km/hr

27. Graphing Motion What would happen … if we graphed
distance something traveled vs
the time it took to travel that distance ?

28. Graphing Motion
Title of Graph
dx vs. time
Headings dx
(ft)
time (s)

29. Graphing Motion John walks 5 ft in 5 seconds dx vs. time dx (ft)
time (s)

30. Graphing Motion John then rests for 5 seconds dx vs. time dx (ft)
time (s)

31. Graphing Motion John walks 2 ft in 2 seconds dx vs. time dx (ft)
time (s)

32. Graphing Motion John then rests for 3 seconds dx vs. time dx (ft)
time (s)

33. Graphing Motion John then runs 5 ft in 2 seconds dx vs. time dx (ft)
time (s)

34. Graphing Motion John then rests for 3 seconds dx vs. time dx (ft)
time (s)

35. Graphing Motion dx vs. time Slope = rise = 7 ft = 1 ft run 7 s s
Speed = 1 ft/s (slope) dx
(ft)
time (s)
The slope of a line on a distance-time graph is speed

36. Graphing Motion Cannot have a negative slope!!! Therefore, can’t have
a negative speed!!
dx vs. time dx
(ft)
time (s)
The slope of a line on a distance-time graph is speed

37. Classroom Quiz 5.1
You walk 5 miles north, 4 miles west and 8 miles south. What is your distance walked and displacement from your starting point? You must draw a diagram