Measuring Line Segments
We have learnt in the previous section about line segments. A triangle is made of
We saw that a line segment is a
To compare any two line segments, we need to find a relation between their lengths.
This can be done in several primitive ways.
Comparison by observation
Comparison by observation is a simple and useful method only when the difference in the lengths is very obvious i.e. a large margin of difference.
Using tracing paper, we trace the line segments.
- Comparison by Tracing
Click on the red line segment and click on the copy icon. Now, try to align the two separate segments such that they overlap each other. This same concept is used when trying to measure the lengths of different line segments.
Are the two line segments given below of equal length?
We can see that the accuracy of the method (for measurment of line segments) depends heavily on how well the tracing has been done. Also, we come to an understanding that the method is time-consuming and not very efficient. Thus, we need a better method.
Comparison using Ruler and a Divider
Have you seen or can you recognise all the instruments in your instrument box? Among other things, you have a ruler and a divider.
Note how the ruler is marked along one of its edges. It is divided into 15 parts. Each of these 15 parts is of length 1cm.
Each centimetre is divided into
Each subpart of the division of a cm is
1 mm is
2 mm is
2.3 cm will mean
In the above drawing panel Place the zero mark of the ruler at A. Read the mark against B. This gives the length of AB.
Suppose the length is 5.8 cm, we may write, Length AB = 5.8 cm or more simply as AB = 5.8 cm.
There is room for errors even in this procedure.
The thickness of the ruler may cause difficulties in reading off the marks on it.
Positioning Error
The angle at which we measure is very important. In order to minimize, especially due to the position of our eye, always view the scale marks from just vertically above(90O angle). Otherwise, angular viewing errors will arise.
