Fundamental and derived
Fundamental and derived units are the two classifications of system of units.
Fundamental Quantities: The physical quantities that do not depend upon the other quantities are the fundamental quantities.
Derived Quantities: The physical quantities that depend upon the fundamental quantities are known as the derived quantities.
Length, Mass, Time
The measurement of physical quantities is one of the most important operations in engineering. Every quantity is measured in terms of some arbitrary, but internationally accepted units, called fundamental units.
All physical quantities, met within this subject, are expressed in terms of the following three fundamental quantities :
1. Length (L or l ),
2. Mass (M or m), and
3. Time (t).
Meter
MKS is the system of units based on measuring lengths in meters, mass in kilograms, and time in seconds.
25.4 mm
25.4 millimetres are there in 1 inch.