Distance Time Graphs
Understanding and
interpreting
Distance Time
Graphs
• Describing a journey made by an object is not exciting if
you just use words. As with much of science, graphs are
more revealing.
• Plotting distance against time can tell you a lot about a
journey. Let's look at the axes:
•
•
Time always runs horizontally (the x-axis). The arrow shows the
direction of time. The further to the right, the longer time from
the start.
Distance runs vertically (the y-axis). The higher up the graph we
go, the further we are from the start.
Not moving? This is what it
looks like…
If something is not moving, a horizontal line is
drawn on a distance-time graph (dt-graph).
• Time is increasing to the right, but its distance
does not change. It is stationary.
Moving….
If something is moving at a steady speed, it
means we expect the same increase in
distance in a given time:
• Time is increasing to the right, and
distance is increasing steadily with time.
It moves at a steady speed.
Steady Speed…
• If something is moving at a steady speed, it
means we expect the same increase in
distance in a given time:
• Time is increasing to the right, and distance
is increasing steadily with time. It moves at a
steady speed.
Can you describe what is going on
here?
• For the first part of the journey shown by the graph
below, the object moved at a steady (slow) speed.
• It then suddenly increased its speed, covering a
much larger distance in the same time.
• This sort of motion is not very realistic, but is
easy to understand. It also makes calculations
easier!
What is the effect of line
‘Steepness’, A.K.A slope…
• Both the lines below show that each object moved the same
distance, but the steeper yellow line got there before the other
one:
• A steeper gradient indicates a larger distance moved in a
given time. In other words, higher speed.
• Both lines are of constant gradient, so both speeds are
constant.
The line below is curving upwards. This shows
an increase in speed, since the gradient is
getting steeper:
In other words, in a given time, the distance
the object moves is larger. It is
accelerating.
There are three parts to the journey shown
below:
• Moving at a steady speed, slowly
Not moving for quite some time
Moving again, but at higher speed
• In all the graphs so far, we have not seen
any numbers - it's about time we did!
Finding speed from these types of
graphs!
• We can see that the motion shown by the yellow line
is fastest.
• By definition, speed = distance / time so the
steepness (or gradient) of the line will give us
the speed!
• Yellow: speed = distance / time = 30 m / 10 s = 3
m/s
• Blue: speed = distance / time = 20 m / 20 s = 1
m/s
Calculate the speeds of different
sections within a graph
• Stage 1: speed = distance / time = 100 m / 10 s =
10 m/s
• Stage 2: speed = distance / time = 50 m / 10 s = 5
m/s
• Stage 3: speed = distance / time = 150 m / 20 s =
7·5 m/s
Lets look at the Textbook!
P. 365 -2, 3, 5, 6