A 60 min lesson on motion - speed, distance and time.

1. Objectives
At the end of this lesson, students will be able to:
1.Explain the relationship between
• Distance,
• Speed and
• Time
2.Use spreadsheets to show relationships and
present information clearly and/or succinctly
3. Draw appropriate type of graph, using excel,
to convey information

2. Motion
Motion is movement.
 Many objects around us can move and if the speed of
these Objects can be determined, then their motion can
be measured.

3. Distance
Distance is how far it is between two points and is
measured in metres (m), kilometres (km) Or
millimetres (mm).
• The choice of unit would depend on how far is the
Distance to be or measured.
• Other multiple units often used in distance
measurement include mirometres (μM) and
nanometres (ηM)

4. Time
Time is a measure of how long it takes between two
events.
• It is often measured in seconds (s), minutes (min),
hours (h), days and weeks.

5. Speed
Speed is defined as how fast an object is moving or the
distance travelled in a given time
• Speed is measured in metres per second (m/s) or in
the case of a car, in kilometres per hour (km/h)
Velocity is speed in a given direction. The measurement
of velocity is important for ships at sea, aircraft and
inter-planetary space probes as it tells the speed and
direction of motion.

6. • When travelling in a car, the speed changes during the
journey. This may be due to slowing down at a
roundabout, a stop at a traffic light or travelling from a
Suburban road to the freeway etc.
• The speedometer of a car gives the speed of the car at
the instant of looking at it – this is the instantaneous
speed.
• The Police use radar guns to measure the
instantaneous speed of cars in motion on
the road.

7. Average Speed is the speed at which a car would trave
if it went at the same speed throughout a journey.
 The relationship between distance, speed and time
can be expressed as follows:
Average speed = distance travelled/time taken
The relationship between
Distance, Speed and Time

8. Calculating Speed, Distance and
Time
Speed =
Distance
Time
Distance = Speed ´ time
Time =
Distance
Speed

9. For example:
1. If a car travels 120km in 2 h, its
Average speed = 120km/2h = 60km/h
Or,
2. If Joan drives at an average speed of 45km/
on a journey of 135km, the journey would take:
Time = 135km/45km/h = 3 hours.
Or
3. Chris cycles at an average speed of 8km/h 3 hours. He travels
a
Distance of 8km/h x 3h = 24km.

10. DISTANCE-TIME GRAPHS
 Distance-time graphs can be used to describe journeys. This ty
of graph is plotted with distance on the vertical (y) axis and time
on the horizontal (x) axis.
The graph below describes 3 parts of a journey:

11.  In the above graph, the gradient of the straight line is a measure of the speed of the
moving object
Note: negative gradient would indicate that the object is moving towards the starting poin

12. EXAMPLES
1. The following graph describes the journey of a snail.
a. Describe the motion of the snail.
b. What is the speed of the snail during each part of the journey?
MEP Y8 Practice Book B18.4
Example 1
The graph shows how far a child is from home.
Distance
(m)
200
400
0
600
800
1000
0 20 40 60 80 100 120 140 160 180 200
Time (seconds)

13. Solution:
a. The first part of the graph showed that the snail travelled away from the start point
for 1000 m in 80 s, at a constant speed.
The second part (horizontal) shows that the snail stopped for 20 s.
The third part shows the snail returning to the start point at a constant speed and
taking 100 s to do so.
b. During the first stage, the snail travelled with a:
Speed = 1000m/80 s = 12.5 m/s.
During the second stage, the speed of the snail was 0 as it was at rest.
And finally, the snail returned to the starting point at a
Speed of 1000 m/100 s = 10 m/s.

14. Speed-Time Graph
 Speed-Time graphs are used to describe the distance travelled by an object.
 They are plotted much the same like Distance-Time graphs. Time as the
independent variable is plotted on the x-axis while speed is plotted on the y-axis
 Speed-Time graphs are also called Velocity-Time graphs.
Motion Graphs 7
SPEED-TIME GRAPHS
Speed-Time graphs are also called Velocity-Time graphs.
Speed-Time graphs look much like Distance-
Time graphs. Be sure to read the labels!!
Time is plotted on the X-axis. Speed or
velocity is plotted on the Y-axis.
A straight horizontal line on a speed-time
graph means that speed is constant. It is
not changing over time.
A straight line does not mean that the
object is not moving!
This graph, with a straight horizontal line shows constant speed

15. This graph shows increasing speed.
The moving object is accelerating.
This graph shows decreasing speed.
The moving object is decelerating.
This graph shows increasing speed.
The moving object is accelerating.
This graph shows decreasing speed.
The moving object is decelerating.
The graph shows that the speed of the
object is increasing or the object is accelerating.
This graph shows that the speed of
the object is decreasing or the object is decelerating.
In summary:

16. http://youtu.be/AcByglYNCqw
Please watch the YouTube video below to refresh your memory o
how to use excel to plot Distance-Time Graphs.
Note that the data set used in the video will be different from the
one in your topic test but the concept for plotting the graph is the
same.
In preparation for your class task:

17.  Please logon to your group page on edmodo and complete the task in your.
 This assignment will count for 10% towards your term 2 assessment and is
due .