# Physics for Competitive Exam ,Part-I

Physics Part-I
Science for Competitive Exam

Units of  physical quantity
What is Unit?
The word which is used to express the standard measure of a quantity is called  Units.
There are usually two types of units:-
Fundamental Units:  Fundamental units are basic units if some physical quantities are expressed in terms of units and these units are independent of each other, then these units are called Fundamental unit. Fundamental units are independent.
Units of Length, mass, Time etc are fundamental units.

Derived Units: If a physical quantity is expressed in terms of two or more fundamental units then the unit is called a derived unit. Derived units have no independent existence.
Units of Force, density, work etc are Derived units.

Physical Quantity is measured in four unit system-
a.  CGS system(Centimeter Gram Second ).
b.  MKS system (Meter Kilogram Second system ).
c.  FPS system ( Foot Pound Second system ).
d.  SI system (International system of units).

In the SI unit system, there are seven (7) fundamental SI unit and these are given below –

 Physical Quantity SI Unit Length Meter Mass Kilogram Time Second Current Ampere Temperature Kelvin Luminous Intensity Candela Amount of substance Mole

Also, there is two Supplementary SI unit-
 Physical Quantity SI Unit Plane Angles Radian Solid Angles Steradian

Some Important SI units are given below-

·             SI unit of Acceleration –Metre/sec2
·        SI unit of Area-m2.
·        SI unit of Astronomical Distance- Lightyear
·        SI unit of Absolute Temperature-Kelvin
·        SI unit of Atmospheric pressure-Bar.
·        SI unit of Angular velocity-rad/Sec
·        SI unit of Acceleration due to gravity –m/sec2.
·        SI unit of Density- Kg/m3
·        SI unit of Electric Current-Ampere
·        SI unit of Electric Charge-Coulomb
·        SI unit of Electric Resistance-Ohm
·        SI unit of Electric Power-kWh (Kilowatt Hour )
·        SI unit of Electric Potential -Volt
·        SI unit of Electric Field Intensity –Newton/Coulomb
·        SI unit of Electric Capacity - Farad
·        SI unit of Frequency –Hertz (Hz)
·        SI unit of Force-Newton
·        SI unit of Heat- Joule.
·        SI unit of Latent Heat-Joule/K.
·        SI unit of Length –Meter.
·        SI unit of Luminous Intensity-Candela.
·        SI unit of Linear Momentum-Newton-Second.
·        SI unit of Mass--Kilogram
·        SI unit of Moment of Inertia-Kg. m2.
·        SI unit of Magnetic Flux –Maxwell, Weber.
·        SI unit of  Magnetic dipole moment-Ampere-meter
·        SI unit of Magnetic Field-Tesla
·        SI unit of Power of Lens-Dioptre
·        SI unit of Power- Joule/Second
·        SI unit of Potential Difference- Volts
·        SI unit of Pressure- Pascal.
·        SI unit of Plane Angle- Radian
·        SI unit of Speed- Meter/Sec
·        SI unit of Surface Tension-Newton/meter
·        SI unit of Solid Angle-Steradian
·        SI unit of  Moment-Kgm²/s²
·        SI unit of Time--Second
·        SI unit of Temperature-Kelvin.
·        SI unit of Volume—m3
·        SI unit of Velocity- Meter/Sec
·        SI unit of Viscosity-Newton. Sec /m2.
·        SI unit of Work- Wavelength-Newton. Meter or Joule.
·        SI unit of Weight- Newton

Some formulae of Physical quantity:-

1.     Area=Length x Breadth.
2.     Volume= Length x Breadth x Height.
3.     Velocity=Distance/Time.
4.     Acceleration=Velocity/Time
5.     Force=Mass x Acceleration.
6.     Work=Force x displacement.
7.     Pressure=Force/Area
8.     Kinetic Energy=1/2 x Mass x(Velocity )2.
9.     Potential Energy =Mass x Acceleration due to gravity x Height.