11. notes on speed graphs
TRANSCRIPT
Speed Graphs
Objectives: SWBAT 1. Recognize distance vs. time graphs;2. Know that distance vs. time graphs
shows the speed;3. Read and interpret graphs.
Standards 1f: Students know how to interpret graphs of position vs. time for motion in single direction.
Examples: Distance vs. Time Graph:
1. Describing the Distance vs. Time Graph:
Y-axis
X-axis
Distance is on the Y-axis!
Time is on the X-axis!
D vs T Graph
Slope of a Distance vs. Time Graph
2. What does the slope show?
Slope of a distance vs. time graph gives the SPEED of the object.
How the graph looks like…
What the graph is telling about the motion…
Draw here the graph…
you will need your ruler!
Write here what the graph means…
Graph 1: Example of D vs T Graph: Horizontal Line
How the graph looks like…
What the graph is telling about the motion…
Time at x-axis
Dis
tan
ce a
t y-
axis
The object is at rest.
(graph is a straight
horizontal line)
Note that the time is increasing to the right, but its distance does not change at all.
What are examples of this motion?
The object is at rest.
Parked cars…
Persons waiting in line and the line is not moving…
Graph 2: Example of D vs T Graph: Straight Line
How the graph looks like…
What the graph is telling about the motion…
Time at x-axis
Dis
tan
ce a
t y-
axis
The object has CONSTANT
speed. (straight lines represent
constant speed)Note that the time is increasing to the right, but distance is increases with the same amount every equal amount of time.
What are examples of this motion?
The object traveling at constant speed.
Cars on the freeway maintaining 60 or 80 mph.
Graph 2: Example of D vs T Graph: Steeper Straight Line
How the graph looks like…
What the graph is telling about the motion…
Time at x-axis
Dis
tan
ce a
t y-
axis
The object with RED line has CONSTANT speed but speed is
faster than the object with BLUE
line. (straight lines represent
constant speed)Note that the RED line took shorter amount of time to cover the same distance, so it is faster.
What are examples of this motion?
Objects that cover the same distance with different amounts of time.
Car Racing!
Graph 3: Example of D vs T Graph: Curve Upwards
How the graph looks like…
What the graph is telling about the motion…
The object increases its speed (speeding up or accelerating)
Note that it covers more and more distance for every equal amount of time.Time at x-axis
Dis
tan
ce a
t y-
axis
What are examples of this motion?
Objects that are speeding up or accelerating.
Start of a run…
Graph 4: Example of D vs T Graph:Curve Downwards
How the graph looks like…
What the graph is telling about the motion…
The object decreases its speed (slowing
down).
Note that it covers less and less distance for every equal amount of time.Time at x-axis
Dis
tan
ce a
t y-
axis
What are examples of this motion?
Objects that slowing down.
A car that is approaching a stop (red) light is slowing down…
Fifth Example of D vs T Graph:Sloping Downward to the X-axis
How the graph looks like…
What the graph is telling about the motion…
Time at x-axis
Dis
tan
ce a
t y-
axis
Both graphs show that the object is going back to its starting point.
Note that both started at distance zero and ended at distance zero.
What are examples of this motion?
Objects that return to their starting point.
You! You go to school everyday but at night, you go back home!
(You are going back to your starting point!)
Summary
1. A means the object is not changing its position - it is or
.
2. A graph with means the object is traveling at .
3. The the line of the graph, it means that the object’s speed is
.
4. A graph with of D vs T means the object is changing its speed, either the object is or .
5. A graph that has means the object is going back .
Summary
1. A horizontal line means the object is not changing its position - it is not moving, it is at rest.
2. A straight line means the object is traveling at constant speed.
3. The steeper the line of the graph, means the faster is the speed of the object.
4. A curved graph of D vs T means the object is changing its speed, either the object is speeding up or slowing down.
5. A graph line going back to zero distance means the object is going back to its starting point.
Practice
The following are the descriptions that we can use to describe the motion of an object (say, a car):
a. The car is traveling at a constant speed.
b. The car is stopped.c. The speed of the car is
increasing.d. The speed of the car is
decreasing.e. The car is going back to its
starting point.
Graph No. 1: Let’s use what we have learned!
TIME (X-axis)
DIS
TA
NC
E (
Y-a
xis)
A
B
D
C
Graph No. 2: Let’s use what we have learned!
TIME (X-axis)
DIS
TA
NC
E (
Y-a
xis)
A
B
D
C
E
Graph No. 3: Let’s use what we have
learned!
TIME (X-axis)
DIS
TA
NC
E (
Y-a
xis)
A
B
D
C
E
Graph No. 4: Let’s use what we have
learned!
TIME (X-axis)
DIS
TA
NC
E (
Y-a
xis)
A
B
D
C
Using Graphs to find Average Speed
Graph No. 5: Find the average speed from
Point A to D:
TIME (X-axis)
DIS
TA
NC
E (
Y-a
xis)
A
B
D
C
10 m
20 m
30 m
40 m
2 s 4 s 6 s 8 s 10 s
50 m
Graph No. 5: Find the average speed from
Point A to D:
TIME (X-axis)
DIS
TA
NC
E (
Y-a
xis)
A
B
D
C
40 m
80 m
120 m
160 m
10 s 20 s 30 s 40 s 60 s
200 m E