Distance time graph powerpoint -review (1)

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.

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.

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