Transcript Real Life Graphs

Starter:
A) y = x + 1
B) y = x – 1
Real Life Graphs
• Objective: To
understand how
graphs are used to
show relationships
between variables
Must:
Graph of monthly mobile phone charges
Plotting graphs – using a table of values
When we plot a graph we usually start with a table of values.
The values in the table usually come from a formula or
equation or from an observation or experiment.
For example, a car hire company charges £30 to hire a car
and then £25 for each day that the car is hired.
This would give us the following table of values:
Number of days, d
Cost in £, c
1
55
2
80
3
105
4
130
5
155
The cost of the car hire depends on the number of days. The
number of days must therefore go in the top row.
Plotting graphs – choosing a scale
The next step is to choose a suitable scale for the axes.
Look at the values that we need to plot.
Number of days, d
Cost in £, c
1
55
2
80
3
105
4
130
5
155
The number of days will go along the horizontal axis.
The numbers range from 1 to 5.
A suitable scale would be 2 units for each day.
The cost will go along the vertical axis.
The cost ranges from 55 to 155.
A suitable scale would be 1 unit for each £10. We could start
the scale at £30.
Plotting graphs – drawing the axes
We then have to draw the axes using our chosen scale.
Cost (£)
We will need at least 10 squares for the horizontal axis and
13 squares for the vertical axis.
When the scale does not start at 0
we must show this with a zigzag at
the start of the axis.
150
140
130
120
110
100
90
80
70
60
50
40
30
Number the axes.
Label the axes, remembering to
include units, if necessary.
0
1
2
3
4
Number of days
5
Plotting graphs – plotting the points
Use the table of values to plot the points on the graph.
1
2
3
4
5
Cost in £, c
55
80
105
130
155
Cost (£)
Number of days, d
Cost of car hire
150
140
130
120
110
100
90
80
70
60
50
40
30
0
It is most accurate to use a small
cross for each point.
If appropriate, join the points
together using a ruler.
Lastly, don’t forget to give the
graph a title.
0
1
2
3
4
Number of days
5
Science experiment
A group of pupils are doing an experiment to explore the
effect of friction on an object moving down a ramp.
They attach weights of different mass to the object and
time how long the object takes to reach the bottom of
the ramp.
They put their results in a table and use the table to plot
a graph of their results.
Mass of object moving down
ramp (grams)
100
150
200
250
Time taken for object to move
down ramp (seconds)
4
7
12
17
Time taken (seconds)
Science experiment
Mass of object moving down
ramp (grams)
100
150
200
250
Time taken for object to move
down ramp (seconds)
4
7
12
17
We can join the points
using straight lines.
20
16
Do the intermediate
points have any practical
significance?
12
8
4
0
0
50 100 150 200 250 300
Mass of object (grams)
How could we make the
graph more accurate?
Class Work
• Frameworks (9) Page 75 Read Exercise
5b- Question 1,2,3 Pg 77 &Exercise 5c 1
is a must