+SI Units

The system of units used in engineering and science is the Systeme Internationale

d’Unites (International system of units), usually abbreviated to

SI units, and is based on the metric system. This was introduced in 1960

and is now adopted by the majority of countries as the official system of

measurement.

The basic units in the SI system are listed with their symbols, in

Table 1.1.

Derived SI units use combinations of basic units and there are many of them.
Two examples are:

• 
  
  Velocity—metres per second (m/s2)
• Acceleration—metres per second squared (m/s2)
  
 

SI units may be made larger or smaller by using prefixes which denote

multiplication or division by a particular amount. The six most common

multiples, with their meaning, are listed in Table 1.2.