When we measure an object we quantify an attribute of the object such as,
the length of a pencil,
A measurement always consists of a number and a unit. For example, that pencil is 4.3 cm long. The area of the yard is 100 m2.
The International System of Units has defined a metric system of units to measure all physical quantities in the universe.
Three of the seven basic SI units are relevant to our everyday experiences. They are:
NOTE: These are standard abbreviations, other abbreviations which are strictly not correct are used occasionally. As teachers we need to make an effort to adhere to the standard abbreviations but accept other common forms.
Common prefixes for SI units
We can combine these basic units with prefixes to form a unit multiple of more convenient size. See the table below for some of these commonly used prefixes.
Because the metric system is based on 10 and its multiples we can easily alter the measurements to larger or smaller units. For example, to convert metres to centimetres we merely need to multiply by 100.
Primary school measurement topics include:
The measurements of length, area, mass, volume and capacity use, or are derived from, the basic SI-units metres and kilograms.
Some Non-SI units have been retained because of their practical importance. In Australia, there is common usage of the following Non-SI units:
Strictly speaking, 'tonne, 'litre' and 'hectare' are metric but not SI units. (The alternative SI terms, which are not commonly used, are, Mkg, 1 dm3 and 10000 m2, respectively.)
Nonstandard units such as an arm's length or a long stride are often used when we want to estimate the length of something. For more information click here to go to Estimation in Key Ideas.
1. How many metres in a kilometre?
2. How many microseconds in a second?
3. What unit would you use to measure the following?
(a) The length of a large table
(b) The volume of a large bottle of cordial
(c) The length of a baby
(d) The time taken to run 100 m
(e) The mass of a large dog
4. Which one of the following is an SI unit?
A. Degrees B. Celsius C. Tonne D. Second E. Hectare F. Litre
5. Which is heavier A kilogram of bricks or a kilogram of feathers? Give a reason for your answer.
To go to the quiz answers, click here.
University of Melbourne