UNIT & DIMENSION

Suppose i ask you "what is 5? what will be your answer? your answer would be " Are you kidding. Is not that obvious."

5 --- is a constant (or) number (or) numeric

10 , 15 20......???? all are numeric

The i add a post-fix to the constant like..

 5 Kg .. what does it sense? It defines a mass or weight..

 10 cm - Length

 15 newton - force

 20 hour  / hr - time

PHYSICAL QUANTITY :

         The quantities which can be measured are called Physical Quantity. Ex : Length , Mass , Time, Volume, Area , etc

UNIT  :

      The Standard of measurement of the physical quantity is called unit . Ex : meter, centi-meter, klio-meter are the unit of length.

SYSTEM :

      A system of units defines a minimum number of physical quantities taken as fundamental to give a consistent and unambiguous description all physical quantity.

      Is it requires for a common international forum of all scientist and engineers concern with measurement.

     There are 4 system in use :-

   1) C.G.S. system 2) F.P.S. system 3) M.K.S. system 4) S.I. system

1) F.P.S. System : The fundamental unit of length , mass, and time are respectively foot (ft), pound (p) and second (s).

2)M.K.S. System : The fundamental unit of length , mass, and time are respectively meter (m),kilo gram (kg) and second (s).

3)C.G.S. System : The fundamental unit of length , mass, and time are respectively centimeter (cm), gram (gm) and second (s).

4) S.I. System : ( International System of unit)

           The S.I. units were approved by the C.G.P.M in 1960 and endorsed by both the ISO( International Organisational for Standardization ) and the IEC ( International Electrotechincal Comission ) in 1967.

           The S.I unit consists of 7 base unit and 2 supplementary unit.

           The S.I. unit are Coherent system of unit. i.e. all other physical quantity are derived from the S.I. units by simple multiplication and division without any numerical.

Base Unit (7)

1. Length - meter (m)

2. Mass   -  kilogram (kg)

3. Time  - Second (s)

4. Temperature - kelvin (k)

5. Luminous Intensity - candela (cd)

6. Electric Current - ampere (A)

7. Amount of substance - mole (mol)

Supplementary Unit (2)

1. Plane angle - radian (rad)

2. Solid angle - steradian (sr)

Example : find the unit of velocity?

     we know velocity = displacement / time

                                   =    m / s = ms^-1

^{Some of the derived physical quantities are} 

DIMESIONS :

         The dimension of a physical quantity are the powers to which fundamental unit must be raised to obtain the unit of that quantity.

DIMESIONAL FORMULA :

         It is a formula which tells how and which of the fundamental units have been used for the measurement of that unit.

DIMESIONAL EQUATION :

       An equation written in the following manner is called dimensional equation .

Example :

a) Area = length x breadth = [ L x L ] = [ L²] = [ M⁰L²T⁰ ]

 1. Dimension of area is 0,2,0 of mass , length and time respectively

  2. Dimensional Formula is [ M⁰L²T⁰ ]

  3. Dimensional equation is Area = [ M⁰L²T⁰ ]

b) Acceleration = Velocity / Time = Displacement / time x (time) = Displacement / time ²

                               ^{= L /} T^{2  =} [ M⁰L¹T ^-2 ]

 1. Dimension of area is 0,1,-2 of mass , length and time respectively

  2. Dimensional Formula is [ M⁰L¹T ^-2 ]

  3. Dimensional equation is Velocity = [ M⁰L¹T ^-2 ]

Steps for determination of dimension :

1. Write the formula of the physical quantity of L.H.S. of the equation.
2. Convert all the quantity of R.H.S. into the fundamental quantity Mass, Length and Time .
3. Substitute M, L, and T for Mass, Length and Time respectively.
4. Collect terms of M,L,T and find their resultant power which give the dimension of a quantity in Mass, Length and Time respectively. 

Application of dimensional analysis : 

1. To check the correctness of a given relation .
2. To convert the value of physical quantity from one system to another.
3. To derive a relation between various physical quantity.

        you can ask your queries by commenting below. I will try to solve your problem.

PHYSICS INTRODUCTION

WHAT IS PHYSICS ?

             Physics has been derived from the Ancient Greek word " phusikḗ " which means " knowledge of nature "  . Physics is the study of nature. The way things connects one another.  These connection are underlined by concepts. and those concepts are beautifully expressed in mathematically.

             Each and everything happen in our real world has a secret behind it. Like we wake up and see sun light is all over and when day passes it vanishes and the same thing happen next day , how?  We see some flowers are looking red some are white, how? When we push a thing it moves away, when we pull thing it comes towards, why? If we go nearer to sun we feel mot hot, but at the top of the mountain we feel cold, as the mountain is more close to sun than ground. why? A rocket falls down but satellite does not why? There is a secret behind everything happen in our universe. 

           " The universe is full of magical things patiently waiting for our wits to grow sharper. Physics is the gateway to those magical things. "

             Consider a smart phone.Physics describes how electricity interacts with the various circuits inside the device. This knowledge helps engineers select the appropriate materials and circuit layout when building the smart phone. Next, consider a GPS system. Physics describes the relationship between the speed of an object,the distance over which it travels, and the time it takes to travel that distance. When you use a GPS device in a vehicle, it utilizes these physics equations to determine the travel time from one location to another.

IS IT REALLY IMPORTANT TO LEARN PHYSICS?

            

             Assume you and your mom watching a base ball match, you are really enjoying the match , and your mom feeling bore as she has no idea about the rules of the match. So your mom did not appreciate the match. To enjoying something or to appreciate something you must know the rule behind it. And physics is the rule of nature. If you know the rule of nature you will alive what is going around you. Physics will help you to appreciate the world more.

Life is physics.Every truth, known or unknown, is physics. The best illusion, the most awe-inspiring phenomenon, is physics. It is the foundation on which every one of our achievement, our understanding is built on. After all, the universe is physics! 

 In the beginning i ask " what is Physics? " I was wrong.  The real question is "what is not physics?" . Every thing is all about physics . 

Share your valuable thoughts in comments.. 

ABOUT THE AUTHOR

Hey Friends.

This is Surya Narayan Barik. Oh sorry forgot am an engineer. 

Lets try again…

hi guys i am Er. Surya Narayan Barik . Am from  Cuttack, Odisha. I am an electrical engineer. I am very fun loving, kind, honest. I used to give lecture on physics to 11th, 12th, diploma students.I have been doing this since last three years.For me its not just a pay cheque honestly am really enjoying this.I am software freak. I love programming.

I believe in everything to be short and simple. My life runs upon by my own philosophy.I truly believe upon ” Learning discover our Ignorance ”  because ” We don't know what We don't know ” . The more we  think  we know the less we actually know. Well, I start this blog to give some simple tricks and tips to understanding physics. I just want to pass each and everything i learn. 

After lots of discussion with Younus . I finalize my blog name. Its " Li Physics Kouti " means " My Physics Box ". Li means " my "  (in Arabic) and Kouti means " box " (in Greek). 

Hope you all find it useful. I would love to hear any suggestion and queries from you.

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