# International Standard Units

Rural Technology

The International System of Units (SI) is the modern, revised form of the metric system developed by French people. The SI unit allows easy multiplication when switching among units having the same base but different prefixes. To convert from meters to centimeters it is only necessary to multiply the number of meters by 100. Inversely, to switch from centimeters to meters, one multiplies the number of centimeters by 0.01. Observe scale given in fig.1.1. It gives conversion of various units into meter. For e.g. 1 cm = 0.01m, 1 kilometer = 1000 meter.

## Base unit:

There are two types of SI units, base and derived units. Base units are the simple measurements for time, length, mass, temperature, electric current and light intensity. Commonly used base units are:

## Derived units:

Derived units are made up of base units, for example, unit of speed is m/s, which is combination of unit of distance and time. Commonly used base units and their symbol names are given below: Derived units are calculated as follows: 1) Speed = Distance / time, unit of distance is meter and time is second. Example of Derived units and their symbol names are given in Table below: Therefore, unit of speed becomes m/s 2) Area of square = length * breadth, unit of length and breadth is meter. Therefore, unit of area = m * m = m2

## Intext Questions

1) Convert the following: 50 cm = m 5.5 km = m 1600 m = km 102 mm = m 2) Observe different weight and answer: + = 500g 500g ____ kg

Rural Technology