Units for Measurements
Any physical quantity can be measured and expressed in terms of a number and unit. For example if say that the length of a rod is 5 m, it means that its length is 5 times as large as a certain standard length called metre (unit). Hence for the measurement of a physical quantity, we need a certain reference standard.
The reference standard used for the
measurement of a physical quantity is called a unit.
A good unit should have the following properties:
i) It should be easily available.
ii) It should be invariable (should not change with space
and time).
iii) It should be universally accepted.
iv) It should be reproducible and not perishable.
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The reference standard used for the measurement of a physical quantity is called a unit
Units for Measurements