This document defines key terms related to speed, velocity, distance, and time. It includes: 1) A table comparing the definitions and units of speed, distance, and time. Speed is defined as the rate of change of distance over time. 2) An example calculating the speed of Usain Bolt running 100m in 9.58 seconds (about 10.44 m/s). 3) A discussion of the differences between average speed, taken over a total time and distance, and instantaneous speed, the speed at a single moment in time. 4) Definitions of displacement as the difference between the starting and ending points of a journey, with the direction taken into account, and velocity

1. Speed and velocity
February 16, 2011
Copy and complete the following table:
Quantity Symbol Unit Symbol Equation
Speed
Distance
Time

2. Quantity Symbol Unit Symbol Equation
Speed v
metre per
second
m/s v=d/t
Distance d metre m d=vt
Time t second s t=d/v

3. time
distance
speed =

4. Definition
• Speed is the rate of change of distance
time
distance
speed =

5. t
d
v =

7. 2
2
1
r
m
Gm
mg =
Why I don’t like formula triangles
Now stick that in a triangle…

8. Can you calculate speed?
• Usain Bolt can run 100 m in 9.58 second.
How fast does he run?

9. Worked example
1
-
ms
OR
m/s
44
.
10
58
.
9
100
?
58
.
9
100
=
=
=
=
=
=
v
s
m
v
t
d
v
v
s
t
m
d

10. Two types of speed
• How fast was Usain Bolt running at the
start?
• How fast was he running in the middle?
• How fast was he running at the finish?

11. Average speed
taken
time
total
travelled
distance
total
speed
average =

12. Instantaneous speed
• This is the speed at
any given moment (or
instant!)
• A speedometer in a
car gives the
instantaneous speed
but you would have to
calculate the average
speed (most GPS
systems can do this
for you)

13. Displacement
• The difference between the starting point and
finishing point. It is distance with direction

14. How far does a football travel
during a match?
• Distance: many kilometers
• Displacement: 0

15. Velocity
• The rate of change of displacement
• OR
• How fast you are going in a particular
direction

16. Velocity
t
s
v =

19. Graphing movement
February 16, 2011

20. Learning objective
• Draw and interpret distance-time graphs
• Draw and interpret velocity-time graphs

21. Define these terms…
• Distance
• Displacement
• Speed
• Velocity

22. The Moving Man

31. To do
• Using graph paper draw a distance-time
graph of your journey to school
• Now try a velocity-time graph of the same
journey