1. Measurement : the comparison of any physical quantity with its
standard unit is called measurement.
Unit : It is a reference standard in terms of which any physical
quantity can be measured.
2.
3.
4. Different system of unit used in different parts of world.
The standard unit should be easily reproducible, internationally accepted.
6. Types of physical quantity
Fundamental quantities Derived quantities Supplementary
quantities
These are the basic quantities from
which other physical quantities
where derived.
These type of physical quantities
where derived from fundamental
physical quantities.
7.
8. Astronomical unit (AU) :- defined as the average distance between the center of earth
and the center of sun.
It is used to measure large distances in solar system.
1AU= 1.496x1011 𝑚
9. Light year (ly)- defines as the distance light travels in one year. This unit used to measure
the distance of nearby stars.
1ly= 9.46x1015
𝑚 = 63.235𝐴𝑈
10. Parsec (pc)- defined as the distance associated with one arcsecond of parallax.
This is the largest unit in science.
1pc= 3.086x1016
𝑚 = 206,265𝐴𝑈 = 3.262𝑙𝑦
