SPEED
Speed
 Speed is the
distance an
object moves in
a particular
amount of time.
OR
 How far you go
and how long it
takes to get
there.
How to find the speed of an object
or a person:
Calculate Speed
 Distance /Time (distance divided by
time)
 Try some: calculate the speed
Distance ->
Time
1m
2m
3m
4m
6m
1 hour
2 hours
3 hours
*
Answers
Distance ->
Divided by
Time
1m
2m
3m
4m
6m
1 hour
1m/h
2m/h
3m/h
4m/h
6m/h
1m/h
1.5m/h
2m/h
3m/h
2 hours 0.5m/h
3 hours 0.33m/h 0.66m/h 1m/h
1.33m/h 2m/h *
Average Speed
 Most objects do not move at constant
speeds for very long.
 Race cars change speeds many times
during the race: slower around the
curves and faster on the straight
places.
Graphing Motion
You can show the motion of an object on a
line graph.
Time is on the X-axis (horizontal) and
distance is on the Y-axis (vertical). The 2
numbers are called coordinates of the point.
Moving Man:
http://www.mste.uiuc.edu/Murphy/MovingM
an/MovingMan.html
Graphing Constant Motion
 Constant motion is motion that does
not change.
 That means the object is neither
speeding up or slowing down.
 Constant motion is shown as a straight
line on a graph:
Motion: Constant Motion
Motion: Constant Motion
12
20
Distance (m)
Distance (m)
25
15
10
5
0
10
8
6
4
2
0
0
1
2
3
4
5
Time (min)
6
7
8
9
10
0
1
2
3
4
5
6
Time (min)
7
8
9
10
Constant Motion Graph
 The slope of the line
can be used to
determine the speed
of the object.
 The change in
distance for every
minute on this graph
is constant.
Motion: Constant Motion
25
Distance (m)
 This graph shows
constant motion
because the slope of
the line does not
change.
20
15
10
5
0
0
1
2
3
4
5
6
7
8
9
10
Time (min)
 Speed =
distance
time
 In this graph
Speed = 2 m/min.
Constant Motion continued
 The slope of this line
does not change
either.
 The distance on this
graph stays the
same.
Motion: Constant Motion
12
Distance (m)
 This graph also
shows constant
motion because the
slope of the line does
not change.
10
8
6
4
2
0
0
1
2
3
4
5
6
7
8
9
10
Time (min)
 Speed = d/t = 0/10
= 0 m/min
 So what can be said
about the motion?
 The object is not
moving.
Change in Motion
 Change in motion
can be seen as a
change in the
straight line or as
a curved line.
Motion: Change in Motion
Distance (m)
25
20
15
10
5
0
0
1
2
3
4
5
6
7
8
9
10
7
8
9
10
Time (min)
Motion: Change in Motion
Distance (m)
 When looking at
a graph, you can
tell when motion
changes because
line is not
straight.
80
70
60
50
40
30
20
10
0
0
1
2
3
4
5
Time (min)
6
Change in Motion continued
 Motion is constant
between minutes 0
and 4, 4 and 6, and
6 and 10.
 Even though
between these
points motion is
constant, the
overall motion
changes.
Motion: Change in Motion
25
Distance (m)
 In this graph, there
are three different
types of constant
motion.
20
15
10
5
0
0
1
2
3
4
5
6
Time (min)
7
8
9
10
Change in Motion continued
 Motion is constantly
changing.
 The curve of this
graph shows
acceleration.
 Acceleration is the
increase or decrease
in speed.
Motion: Change in Motion
Distance (m)
 In this graph, the
motion is not
constant between
any two points.
80
70
60
50
40
30
20
10
0
0
1
2
3
4
5
6
7
8
9
Time (min)
 This graph shows
increasing speed
because the curve
goes upward.
10
Change in Direction
 By looking at the
slopes of the two
lines, what can be
said about the speed
before compared to
the speed after
turning around?
Motion: Change in Direction
20
Distance (m)
 On a motion graph,
you can tell when the
object reverses
direction because the
distance from the
starting point
becomes less.
15
10
5
0
1
2
3
4
5
6
7
8
9
10
11
Time (min)
 The speed before
turning around is
quicker because the
_______
is greater
Slope
than after turning
around.
 Line graphs can show all kinds of
information.
 Look at the axis labels before you
analyze the information.
Time Graph
Connect the dots and analyze the graph
600 m race
4
3
3.5
3.5
3
3
3
3
Time
(min)
2.5
2.5
George
2
Nina
1
0
Lap 1
Lap 2
Lap 3
Lap
Lap 4
Analysis: Time Graph
 This is a graph showing time for 2 runners
in the 600 m race. It shows that George
ran 2.5 minutes for the first lap, 3 minutes
for the 2nd lap, 3.5 minutes for the 3rd lap,
and 3 minutes for the 4th lap. Nina ran 3
minutes for the 1st, 3.5 for the 2nd, 3 for
the 3rd, and 2.5 for the 4th. To calculate the
average speed, take the total distance and
divide by the total time.
 George’s average speed: 50 m/min
 Nina’s average speed: 50 m/min