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Dy Handyman
Understanding metrics (6)
NE basic premise of the metric system and :he one that makes it so universally acceptlble is that all larger or smaller units than the Dase unit are multiples or submutiples of 10. This factor consequently makes calculation very much easier.
The metric system has base unit prefixes which inherently state the order of the multiple or submultiple. Some of these are widely used and thus well known, others are not Examples of well-known multiple prefixes are mega and kilo. Mega stands for 1,000,000 and kilo for 1000, thus a one megaton bomb has an explosive power equivalent to 1,000,000 tons of TNT and a one kilogram weight is 1000 times heavier than a gram. Other multiple prefixes such as deca for 10' and giga 109 exist for the sake of completeness, but are only rarely used.
In the same way submultiple prefixes have common and rare usages. The common ones are centi 0.01 or 10-2 milli 0.001 or l0— and micro 0.000 001 or 10-6. Among the rarer ones are nano 10-9 and atto 10-". Centi in centimetre indicates that it is a hundredth part of a metre, milli in millimetre indicates that it is a one-thousandth part of a metre and micro in microampere
Some examples of the more commonly used prefixes are kilometre= thousand metres km millisecond —thousandth of a second ms microampere.= millionth of an ampere p A The only exception to the prefix rules given above is the unit of mass, the kilogram. The use of the multiple and submultiple prefixes infers that the gram is the base unit, and indeed under an earlier system it was, but in fact the kilogram is now the base unit so the megagram is not a million times the base unit as the rule says, but only one-thousand times bigger. This contradiction is not, however, of great consequence. The kilogram was chosen for its practical convenience in favour of the gram and so long as we remember that the name means what it says, it should not cause any difficulty.
MEM ford Street, London SEI 9LU. Because of the substantial demand for the charts not more than six can be supplied to any one applicant.
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11X1111111=1 This exclusive metric conversion chart, which first appeared in Commercial Vehicles, is designed to assist readers wanting to know at a glance the metric equivalent of dimensions, weights and other Imperial measures. The chart covers almost all the figures and measurements encountered in transport operation.
A two-colour version of the chart is available free of charge on application to the editorial department of Commercial Motor at Dorset House, Stam