Preparation Guide to the Indian Civil Services Exam

Physical Quantities:
This is one way of dividing the physical quantities that we encounter:

Division of physical quantities into fundamental and derived quantities.

And this is the second way of dividing them:

Division of physical quantities in terms of vector and scalar

Unit of length:
-> Definition: “Length of path travelled by light in vaccum during the time interval of 1/299792458 of a second”
-> Some units to measure small distances:
(Note: ^ stands for “to the power of”)
1 micron or micrometer = 10^-6 meters
1 nano meter = 10^-9 meters
1 Angstrom = 10^-10 meters
1 Femto meter = 10^-15 meters

-> Some units to measure large distances:
1 light year = 9.46 x 10^15 meters

Unit of mass:
-> Definition: “Mass of a particular solid cylinder of platinum-iridium kept at Sevres

Unit of time:
-> Definition: “Defined using atomic clock which works on energy changes in gaseous cesium atoms.