If you want to read notes related to physics, then you have come to the right place. In this post, we are providing the notes of Basic of Physics, we will prepare for physics from the beginning to the end in which you will be available all the notes absolutely free according to the topic, which you will be able to prepare for any exam easily while sitting at home.
Basic of Physics
Physical Quantities:-
– The quantities which can be measured are called physical quantities.
Types of Physical Quantities
(A) On the basis of units and measurement –
– Units are used to measure any physical quantity.
– There are two types of units –
(i) Basic Unit:-
– Units that do not require other units to be expressed.
– There are seven types of basic units according to the S.I system-
| Principal Amount | Basic Unit | Sign |
| Length | Metre | m |
| Mass | kilogram | Kg |
| Time | Second | S |
| Electric current | Ampere | A |
| Heat | Kelvin | K |
| Light intensity | Candela | cd |
| Amount of substance | Mole | mol |
(ii) Derived unit:-
– Those units, which are obtained with the help of basic units.
| Physical Quantity | Unit |
| Density | kg m-3 |
| Acceleration | m sec-2 |
| Pressure | newton-metre-2 or pascal |
| Work or energy | newton-metre or joule |
| Power | joule sec-1 or watt |
| Velocity | metre sec-1 |
| Force | kg-m sec -2 or Newton |
(B) On the basis of direction and result, there are two types of quantity-
(i) Scalar Quantity:-
– Those physical quantities which require only the result to be expressed, not the direction, are called Scalar Quantities.
Example – distance, speed, time, energy, power, electric current, charge etc.
(ii) Vector Quantity:-
– Those physical quantities which require direction as well as result to be expressed are called Vector Quantities.
Example- displacement, velocity, acceleration, force, electric field, torque, etc.
Unit System
1. MKS System:-
Length – metre (m)
Mass – kilogram (kg)
Time – second (s)
2. CGS System:-
Length – Centimetre (cm)
Mass – gram (gm)
Time – second (s)
3. FPS System:- It is also called British system.
Length – foot
Mass – pound
Time – second
4. SI System (International system of unit)
– This method is a modified form of MKS method.
– This method is used at present.
– The SI system has seven basic units.
Units of Distance
1. Astronomical Unit (AU)
– An astronomical unit represents the average distance between the Earth and the Sun.
1AU = 1.4×1011m
2. Light year –
– Distance covered by light in one year
1LY = 9.46 × 1015m
3. Parsec –
– It is the largest unit of distance.
1 Parsec = 3.08 × 1016m
– It is used to measure the distance between celestial bodies.
Force (F):–
– m×a (m = mass, a = acceleration)
– The unit of force is Newton.
– 1 Newton = 105 dyne
Energy –
– joule, calorie, erg
– 1 joule = 107 arg
Some physical quantities to study motion
Distance and Displacement
| Distance | Displacement |
| (i) The total length of the path covered is called Distance. | (i) The straight distance between the starting and ending points is called Displacement. |
| (ii) It is a scalar quantity. | (ii) It is a vector quantity. |
| (iii)It’s unit is metre. | (iii)It’s unit is meter. |
Speed and Velocity
| Speed | Velocity |
| The distance covered in unit time is called speed. | The displacement traveled in unit time is called velocity. |
| It is a scalar quantity. | It is a vector quantity. |
| Their unit is meter/second. | Their unit is meter/second. |
Acceleration (a):-
– The rate of change of/in velocity of an object in unit time is equal to the acceleration produced in it.
– It is a vector quantity.
– It’s unit is meter/second2 or meter × second-2.
Momentum (P):-
– The product of mass and velocity of an object shows the momentum of that object.
– P = M×V
– It is a vector quantity.
Note : If you are preparing for UPSC, SSC or any other exam then definitely join us.