Physical quantity and units - StudyPCM

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Physical quantity and units

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Hello friends, today we will know about physical quantity and unit. because without it we cannot explain many laws of physics and its explanation.
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What is physical quantity?
Physical quantity is the quantity with the help of many laws of physics we understand and explain it.
Force,mass, density, acceleration , velocity , current ,length ,pressure ,frequency etc all are the example of physical quantity.
What is unit?
The standard of measurement of a physical quantity is known as unit.
For example, if we measure Mass of some mangoes , we can't understand how much is its mass so we use units of mass to understand physical quantity clearly.With the help of unit we can determine quantity like 4kg mangoes, 2m length of cloths ,4 hour etc.

There are two types of physical quantities.
A. Fundamental physical quantity- Those physical quantities which are independent is called fundamental physical quantity. They are 7 in number.
Image result for si units
  1. Mass - kilogram(kg)
  2. Length - meter(m)
  3. Time - seconds(s)
  4. Current- ampere(A)
  5. Temperature - kelvin(k)
  6. Amount of quantity - mole(mol)
  7. Luminous intensity - candela (cd)
B. Derived physical quantity - Those physical quantity which is derived from fundamental physical quantity is called derived physical quantities.Speed ,velocity,density,work ,power,pressure, force etc are the example of derived physical quantity.

 For example - speed derived physical quantity because it is derived from length and time .
 Speed = distance (length)/time
Its unit is m/s.

Types of unit.
1. Fps or British system 
    Length - foot
    Mass - pound
    Time - second
2. C.g.s system
    Length - centimetres
    Mass - gram 
    Time - second
3. M.k.s system or S.I. system
    S.I. - System of international 
    Length - metre
    Mass - kilogram
    Time - second


Some important  abbreviation 
Image result for si units

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