Graphing motion notes from 9/14

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
yellowyellow.

11.  YellowYellow: speed =
distance / time =
30 m / 10 s = 33
m/sm/s
 BlueBlue: speed =
distance / time =
20 m / 20 s = 11
m/sm/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: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:Stage 2: speed = distance /
time = 50 m / 10 s = 5 m/s5 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: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: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