This document explains how to interpret distance-time graphs. It discusses that distance is plotted on the y-axis and time on the x-axis. A horizontal line indicates no movement, a straight upward sloping line indicates constant speed, and a curved line shows changing speed. Steeper lines correspond to higher speeds as they represent greater distance covered in the same time. The direction of the line also shows if an object is moving away from or toward the starting point. Examples are provided to illustrate constant, changing, and stopping speeds.

1. Distance vs. Time

2.  Describing a journey made by
an object is very boring 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.

3.  Let's look
at the axes:

4.  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.

5.  Distance runs
vertically (the y-
axis). The higher
up the graph we
go, the further
we are from the
start.

6.  If something is not moving, a
horizontal line is drawn on a
distance-time graph.
 Time is increasing to the
right, but its distance does
not change.
 This graph shows an object
that is stationary.

7.  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.

8.  This graph
shows an
object that
moves at a
steady,
constant speed.

9.  Both the lines below
show that each object
moved the same
distance, but the steeper
yellow line got there
before the other one.
 What does this indicate?

10.  A steeper slope
indicates a larger
distance moved in a
given time. In other
words, higher
speed.
 This is shown in
yellow.

11.  Yellow: speed =
distance / time =
30 m / 10 s = 3 m/s
 Blue: speed =
distance / time =
20 m / 20 s = 1 m/s

12.  For the first
part of the
journey shown
by the graph
below, the
object moved at
a steady (slow)
speed.

13.  Then the object suddenly
increased its speed,
covering a much larger
distance in the same time.
 The speed increased in
the second part of the
journey.

14.  The line below is
curving upwards.
This shows an
increase in speed,
since the slope is
getting steeper
over time.

15.  In other words,
in a given time,
the distance the
object moves is
larger.
 It is
accelerating.

16.  There are three parts to
the journey shown
here… Where is the
graph showing motion
that is:
 Stopped?
 Moving at a quick
constant speed?
 Traveling at a slow
constant speed?
A
B
C

17.  The graph below shows several stages of motion:
Stage 1: 100 m in 10 s.
Stage 2: 50 m in 10 s.
Stage 3: 150 m in 20 s.
Calculate the speeds of
each stage, indicated by the
colors.

18.  The graph below shows several stages of motion:
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.

19.  The graph below shows several stages of motion:
Stage 1: constant speed at a
relatively high rate
Stage 2: constant speed at a
relatively slow rate
Stage 3: constant speed at a
“medium” rate (between the
others)

20.  The graph below shows several stages of motion:
The slope of the line (its
steepness) indicates
rate of change of
position.
Speed can be estimated
by the slope of the
line… faster, slower,
etc.

21.  Distance vs. time graphs also indicate the
position of the object.
Stage 1 & Stage 2: object is
moving away from the starting
point
Stage 3: object is moving back
toward the starting point (it
comes back to zero)

22.  The steeper the line on a distance vs.
time graph, the faster the object’s
speed.
 A curved line indicates a change in
speed (accelerating or decelerating).

23.  Lines pointing up indicate moving
away from the starting location.
 Lines pointing down indicate moving
back towards the starting location.

24.  Let’s see how much this makes
sense to you…
 This is not for a grade, just to let me
know how much of this and what
parts of it you “get.”

25.  To learn about speed vs. time
graphs, visit this link:
http://www.gcse.com/fm/stg.htm