Metre stick Trundle wheel Opisometer Vernier calliper Micrometer Area
Measuring Length and Area Learning Intentions
In this topic we are learning to: z Describe how to use various instruments for measuring length. z Measure and calculate the area of a regular and irregular shape.
The instrument you choose to measure with depends on the scale and size of the quantity you are trying to measure.
For example, if you are trying to measure the length of a football field, a ruler from your pencil case might not be the best tool. Or if you are trying to measure the length of the centre circle on a football field, a straight object such as a metre stick would not accurately measure the curve of the line.
Fig. 15.2.1 Overhead view of a football field Measuring Length
The SI unit for length is metres (m). There are many instruments that can be used to measure different lengths.
z For measuring the length of straight lines, you could use a ruler, a metre stick, a measuring tape or a trundle wheel.
z For measuring the length of curved lines, you could use an opisometer (for short lines) or a trundle wheel (for long curved lines).
z For measuring widths, thicknesses and lengths of small objects, you could use a Vernier calliper or a micrometer.
Fig. 15.2.2
A worker measuring distances with a trundle wheel as part of work to lay a new water pipe
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Fig. 15.2.3
An opisometer is traced along the curved line. It is then placed next to a ruler and drawn back to its zero point in a straight line. The length of this straight line is the same as the length of the curved line
Fig. 15.2.4 A Vernier calliper being used to measure the
diameter of a bolt
Fig. 15.2.5 A micrometer being used to measure the thickness of a coin
