Distance-Time
Graphs
2016-2017
Review - Speed
Speed:
- The measure of how fast/slow something moves a particular distance over a
given amount of time.
- It can then be calculated using the following formula:
- v=d/t
How do you graph speed?
Graphs are always set up the same way:
Y - axis
X- axis
Distance - Time Graphs
On a distance time graph, the distance will always be the dependent variable on the
y- axis. Y - axis
X- axis
Time is the independent variable and will always be placed on the x-axis.
Lines on the Graphs
The lines on the graphs can tell you many different things. For example:
The slope of a line (steepness) can tell you speed.
If the slope is steep (more vertical) then the speed is fast.
If the slope is flatter (more horizontal) then the speed is slow.
If the line is completely flat or horizontal then the object has no speed or is stopped.
Examples of distance-time graphs
FAST
STOPPED
SLOW
Other things we can learn from a graph:
We can also show the direction the object is traveling. The point on the graph where
the x and y axis meet is the reference point or where the object’s home base is
located (their starting point).
If the arrow or line is pointing away or moving away from the x axis then the object
is moving away from their reference point or starting point.
If the arrow or line is pointing toward or moving toward the x axis then the object is
moving back to the reference point.
Leaving and coming back:
Speeding up and Slowing down
The object is speeding up and has positive
acceleration.
The object is slowing down and has
negative acceleration.
Practice reading graphs
Determining Speed from a graph
V=d/t
1. Think of the graph in sections divided
by each line segment
2. Then determine the total distance for
the line segment you are looking at.
3. Then determine the total time for that
segment.
4. Finally, use the equation to determine
speed of the line segment.
Example: the object traveled a total distance of 25 m for the first segment. It took
the object 20 seconds. v=d/t v=25/20 v= 1.25 m/s
Practice
Calculate the speed for last line segment:
1.
2.
3.
4.
Distance traveled = 25 m
Time = 10 sec
v=d/t 25/10
2.50 m/sec
Was the object moving faster or slower than when
they started?
Practice on your own:
1. Calculate the speed for the first
segment.
2. Calculate the speed for the third
segment.
Graphs and Stories
This object left the reference point at a
fast constant pace.
They then stopped for a brief period of
time.
Finally they began to move again but at
a slower rate.
Example with stories
Joe left home at a moderate constant
speed. He realized that he forgot his wallet
and turned around to go home to get it.
However, while walking back he realized it
was in his pocket so he turned around to
head back to his friend’s house. He picked
up his pace a little to help make up some
lost time. When he got to his friend’s
house they stayed to watch a movie.
Distance
(m)
You Practice writing a story