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Measurements
To Measure
the Slope of a Graph
The slope of a
graph tells us how a change in one variable affects the
value of another variable.
To measure the slope, proceed
as follows.
| 1. |
Find
out what one small square represents
vertically. For example, one small square might
represent 0·01volts or 10metres etc. This is the
vertical scale. |
| 2. |
Find
out what one small square represents
horizontally. For example, one small square might
represent 0·002Amps or 0·5seconds etc. This is the horizontal
scale. |
| 3. |
Count
the number of small squares, Ny, between y1
and y2 (see diagrams below), and work out
the change that this figure represents.
vertical
change = Ny × (vertical scale) |
| 4. |
Count
the number of small squares, Nx, between x1
and x2 (see diagrams below), and work out
the change that this figure represents.
horizontal
change = Nx × (horizontal scale) |
| 5. |
Now,
the slope of the graph is defined as
and must, of
course, be stated in the appropriate
UNITS |
(x1,y1)
and (x2 ,y2) can be the co-ordinates of
any two points on the line but for best precision, they
should be as far apart as possible as shown in the two
examples below.
In the second graph, it is
clear that y decreases as x increases so in this case, the
slope is negative.
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© David
Hoult 2008 |
The
Open Door Web Site 
