Page 1 - Lesson Notes-Standard unit of measurement

SAI INTERNATIONAL SCHOOL

Class 6
Lesson notes
Subject- Physics
Ch. - Measurement and motion

Subtopic- Standard units of measurement

Standard Measurement: The measurements which do not vary from person to
person is called standard measurements.
• Standard measuring tools such as ruler, measuring tape, metre rod etc. are
used for standard measurement.
• Standard units of measurement do not vary from person to person.
• Metre, seconds, grams, litre are the units of standard measurement.
SI system of measurement.
• S.I. system- International system of standard units.
• As different countries were using different units for measurement, it created
a lot of confusion internationally among people. To overcome the difficulties
and inconvenience of measurement, people felt the need for standard units
of measurement. So for the sake of uniformity SI Unit was developed and all
the people accepted the System internationally.

Different system of units is:
MKS system: - metre for length, kilogram for mass, second for time.
CGS system: - centimetre for length, gram for mass, second for time.
FPS system: - foot for length, pound for mass, second for time.
(Note: Generally, all SI units are based on MKS system.)

Advantages of the SI system-
1) It is a universally accepted standardise set of units.
2) Even very small measurements are possible in this system.
3) Inter-conversion within the system is simple, and hence calculations are easy.
4) The units do not change with system.

Example: SI unit of length is metre
• To measure large lengths such as the distance between two cities we use
kilometre.
• To measure smaller lengths such as the thickness of a book, width if the screen of
a mobile we use centimetre (cm) and millimetre (mm).