Speed 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