Distance and displacement

1. OBJECTS IN MOTION.
01. Distance and displacement.
Ian Anderson
Saint Ignatius College Geelong

2. DISTANCE V DISPLACEMENT.
How far do you think you walk every day while at
school between homeroom in the morning and
homeroom in the afternoon?

3. DISTANCE V DISPLACEMENT.
What would you say if I said you walked
0 m?
It’s true! Your displacement between
morning homeroom and afternoon homeroom
is zero. Although the distance you walked is
probably closer to around
2500 m.
So what is the difference between distance
and displacement?

4. DISTANCE V DISPLACEMENT.
Follow the clues on the treasure map to find the buried
treasure.
Source: Sharwood (2006)

5. DISTANCE V DISPLACEMENT.
How many paces have you walked when you get to the
treasure?
Answer = 3200 paces.
Source: Sharwood (2006)
How many paces are
you actually away from
your landing point?
Answer = 200 paces
to the west.

6. DISTANCE V DISPLACEMENT.
How many paces have you walked when you get to the
treasure?
Answer = 3200 paces.
How many paces are
you actually away from
your landing point?
Answer = 200 paces
to the west.
Source: Sharwood (2006)

7. DISTANCE.
Distance is a measure of how far an object travels
over a certain period of time.
3200 paces in our pirate treasure example.
Distance can be measured in any length units,
including kilometres or millimetres, but is usually
converted into metres.
Metres (m) is the SI unit for distance.
Distance is a scalar quantity because it only has size
but no direction.

8. DISPLACEMENT.
Displacement describes the change in position of an
object and its direction over a certain period of time. It is
the shortest distance between the initial point and the final
point.
200 paces West in our pirate treasure example.
The SI unit for displacement is metres (m). The direction
of the change in position can be described using compass
points (N, S, E or W); left or right; or positive (+) or
negative (-).
Displacement is a vector quantity because it has size and
direction.

9. POSITION-TIME GRAPHS.
 Position-time graphs (also called displacement-time
graphs) show the total distance travelled by an
object over time.
Position-time graphs can be used to determine
 The displacement of an object at any point in time.
 The speed or velocity of an object at any point in time.

10. POSITION-TIME GRAPHS.
 Position-time graphs (also called displacement-time
graphs) show the total distance travelled by an
object over time.
Position-time graphs can be used to determine
 The displacement of an object at any point in time.
 The speed or velocity of an object at any point in time.

11. POSITION-TIME GRAPHS.
Position-time graphs show
the total distance covered by
an object as time
progressed.
The object first covers a
distance of 4 m in 6 s,
stops for 2 s, before setting
off again for a distance of 8
m in 4 s, before finally
resting for another 3 s. The
total distance covered was
12 m.
Source: Alford et al. (2010)

12. POSITION-TIME GRAPHS.
Position-time graphs can
also be used to determine
the displacement of an
object at any point in time.
At 6 s the displacement of
the object is 4 m N (or +4
m).
The displacement of the
object at the end of the
journey is 4 m S (or
-4 m).
Source: Alford et al. (2010)

13. POSITION-TIME GRAPHS.
Use the position-time graph to answer the questions
that follow.
Source: Sharwood et al. (2006)

14. POSITION-TIME GRAPHS.
1. At what time/s was
the object stationary?
Answer =
Between 0 & 30 s and
again between 60 &
80 s.
Source: Sharwood et al. (2006)

15. POSITION-TIME GRAPHS.
2. What was the objects
distance from it’s
starting point at
t=60 s?
Answer =
60 m
Note: At 60 s the object’s
displacement is -20 m
from point (P).
Source: Sharwood et al. (2006)

16. POSITION-TIME GRAPHS.
3. What was the objects
displacement from it’s
starting point at
t=60 s?
Answer =
60 m S
Source: Sharwood et al. (2006)

17. BIBLIOGRAPHY.
Alford, K., Keenihan, S., Malone, J., & Smart, A.
(2010). Big Ideas Science 3: VELS Edition.
Melbourne: Oxford University Press.
Sharwood, J. (Ed.). (2006). Science Edge 4.
Melbourne: Thomson Learning.

18. http://SICkScience10.wikispaces.com/