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Units and dimensions

Physical quantities :The measurement of quantities such as mass,length,volume,temperature and pressure etc.All such quantities which we come across during our scientific studies are called physical quantities.
Unit:The measurement of a physical quantity consists of two parts:
(1).the number and
(2).the unit.
For example,if an object weighs 4kg, it involves two parts;
(1).4 is the number and
(2).kg is the unit.
Fundamental units:
Fundamental units are those units which can neither be derived from one another nor can they be further resolved into any other units.
For example,the quantities mass,length and time are called fundamental physical quantities and their units are known as fundamental units.
Derivation of units:
By using dimensional equations,we can derive the si units of various physical quantities from their basic definitions.
For example:
(1). velocity:velocity is the rate of change of position.
(2). Acceleration:acceleration is the rate of change of velocity.
(3). Force: Force is a push or pull which produces or tends to produce stop or stop
       motion in a body.
       
        Force=mass*acceleration 
  
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