1. International System of Units Measurement It is the process of assigning a number to an attribute (or phenomenon) according to a rule or set of rules. Units A unit is the chosen standard of measurement of quantity, which has the same nature as the quantity. To express any physical quantity completely, we need the numerical value and the unit ( u ). Physical quantity = nu Fundamental Units: Units for fundamental or base quantities (length, mass and time) Derived Units: Units obtained from fundamental units Example: Unit of speed ( ms −1 ) Speed ∴ Unit of speed Systems of Units CGS System: Base units for length, mass and time in this system are centimeter, gram and second respectively. FPS System: Base units for length, mass and time in this system are foot, pound and second respectively. MKS System: Base units in this system are metre, kilogram and second. International System (SI) of Units: Based on seven base units; at present the internationally accepted sy