Units
Mechanics > Units and Vectors
Fundamental units and Derived units Fundamental units and Derived units

Units are standards for measurement of physical quantities that need clear definitions to be useful.

Reproducibility of experimental results is central to the scientific method. A standard system of units facilitates this. Scientific systems of units are a refinement of the concept of weights and measures developed long ago for commercial purposes.

(a) System of units: There are a number of system of units out of which the following three are discussed thoroughly.

  1. CGS (Centimeter Gram Second): The unit of length is measured in centimeters; the unit of mass is measured in grams and the unit of time is measured in seconds.
  2. MKS (Meter Kilogram Second): The unit of length is measured in meters; the unit of mass is measured in kilograms and the unit of time is measured in seconds.
  3. FPS (Foot Pound Second): The unit of length is measured in foot; the unit of mass is measured in pound and the unit of time is measured in seconds.

(b) Fundamental units: There are 7 basic fundamental units of measurement. They are:

  • Length (meters)
  • Mass (kilograms)
  • Time (seconds)
  • Electric current (amperes)
  • Temperature (kelvin)
  • Luminous Intensity (candela)
  • Mole (mol)

(c) Derived units: A unit of measurement that is determined by combining one or more measurements.There are lot of derived units that come from the fundamental units. Many derived units have special names for the properties or measurements they represent. Some of the derived units are

  • Volume (m3)
  • Velocity (m/s)
  • Area (m2)
  • Acceleration (m/s2)
  • Current density(A/m2)
  • Mass density (kg/m3)
  • Magnetic field strength (A/m)

MORE INFO