Measurement of Length: How to Measure Straight and Curved Lines

Measurement of length is a very important concept because it helps us understand how long, tall, or wide an object is. From measuring a book to calculating distances between two different places, the measurement of length plays an important role in accuracy.

In this article, we will understand the unit of measurement length, methods to measure straight and curved lines, and what kind of important precautions should be taken while performing measurements.

Table of Contents

• Understanding Measurement of Length
• Methods for Measuring the Length of a Straight Line
• Methods for Measuring the Length of a Curved Line

Understanding Measurement of Length

Length is the measure of the distance between any two points. The SI unit of measurement length is metre. Measurement of length is a process of measuring the distance between any two points in terms of width, thickness, depth, and height.

Length can be measured using instruments like a metre scale, a metre rule, a measuring tape, etc., or whichever is convenient for the required purpose. 

For example, you cannot measure the circumference of your neck using a metre rod; you will have to use a measuring tape. Tailors use a measuring tape while a cloth merchant uses a metre rod.

Methods for Measuring the Length of a Straight Line

While measuring the length of a straight line or the sharp edge of any object using a ruler, the following procedure must be followed:

1. The ruler should be kept exactly along the length to be measured.
2. The zero mark of the ruler should be placed at one end of the object. Note the reading on the ruler that coincides with the other end of the object. This will give us the length of the object or the straight line.

We tend to make a lot of errors while measuring the length of a line. Those errors can be avoided by taking some precautions.

Important Precautions to be taken to measure the length of a straight line

1. Placement of ruler: The ruler should be in direct contact with the object placed on a flat surface and kept along the length of the object.
2. Proper position of the eye (parallax error): Your eyes must be exactly in front of the point where the measurement is to be taken. As shown in the figure, position B is the correct position.

Looking at the point of measurement from different angles, we might get an error. This error is called parallax error. Position A & C will give you a parallax error.

1. Broken ends: If the end of the scale is broken at the zero mark, you can use any other full mark on the scale. To get the length, subtract the reading of this full mark from the reading of the other end.

Solved Example

While measuring the length of a needle, the reading at one end is 2.0 cm, and the other end is 21.3 cm. What is the length of the needle?

Solution : 

Length of the needle = 21.3 cm – 2.0 cm = 19.3 cm

Methods for Measuring the Length of a Curved Line

Now, an important question arises here: how to measure the length of a curved line? The length of a curved line can be measured using a thread and a divider.

Procedure:

1. Draw a curved line ‘PQ’ on a piece of paper.
2. Make a knot on a thread and place this knot at point P.
3. Align the thread along the curve ‘PQ’. Holding it tight with your finger, trace the path of the curve slowly until you reach point Q.
4. Tie a knot at this point of the thread.
5. Measure the length of the thread using a scale.

This measurement will give you the length of the curved line PQ.

In this article, we have learned how the measurement of length is done using standard units and the methods for straight and curved lines. By following proper procedures and precautions, one ensures accurate results in everyday life and practical activities for measuring length.