Welcome to our blog, where I will teach you **Class 11 Physics Chapter 1**. We will learn about ‘units and measurement’ in the 1st chapter of physics. If you are in class 11 or have an interest in fundamental principles of physics.

## Introduction of Class 11 Physics Chapter 1

In this blog, we will provide you with detailed **Class 11 Physics Chapter 1 notes** that are designed to not only help you understand the subject matter but also serve as a valuable resource for your academic journey. We will learn about the key concepts, equations, and principles covered in this chapter, making it easier for you to score good marks in class 11.

let’s embark on this educational journey together and unlock the mysteries of Class 11 Physics Chapter 1. Let’s begin by exploring the significance of units and measurements in the world of physics.

# Class 11 Physics Chapter 1 Notes

## Define Physical Quantities

Those quantities which can be measured or weighted are called physical quantities.

Example – Length, time, mass, etc.

A physical quantity is represented by the product of numerical value and unit

Quantity = Numerical + Unit (Q = n x u)

The numerical value is inversely proportional to the unit.

n ∝ 1/u

For two quantity-

n₁/n₂ = u₂/u₁ **→** n₁ u₁ = n₂ u₂

### Unit

The specific amount of any quantity by which we measured the quantity is called a unit.

## Types of Physical Quantities

### 1. Fundamental quantities(Physics)

Those quantities that are independent of each other are called fundamental quantities.

#### Fundamental Quantities Example

Meter, seconds, kilogram, ampere, kelvin, mole, candela.

Quantity | Unit |

Length | Meter(m) |

Mass | Kilogram(Kg) |

Time | Seconds(S) |

### 2. Derived Quantities

Those Quantities which depend on fundamental quantities are called derived quantities. They have a finite formula.

Example- Area, volume, speed, distance.

## System of International Units

### 1. MKS System Units

A system in which the length is measured in meters, mass is measured in kilograms, and time is measured in seconds is called the MKS System. It is a French system.

### 2. CGS System Units

A system in which length is measured in centimeter, mass is measured in gram, and time is measured in second are called a CGS System

### 3. FPS System Units

A System in which length is measured in feet, mass is measured in the pond, and time in seconds is called an FPS System Units

## SI System Unit

In 1960 the International Council of Measurement and Weight suggested a single system for all the quantities which is called the SI System unit. It is broad from the MKS System.

Quantity | Unit | Symbol |

Length | Meter | M |

Mass | Kilogram | Kg |

Time | Second | S |

Current | Ampere | A |

Kelvin | Kelvein | K |

Amount of Sub | Mole | Mol |

Luminous Infinity | Candela | Cd |

### Supplementary:-

Quantity | Formula | Unit |

2D Angle | θ = Arc/Radius | Radian |

3D Angle | – | Steradian |

### Derived Quantities

S. No. | Quantity | Formula | Unit |

1 | Area | A = LxB | m x m = m² |

2 | Volume | V = LxBxH | m³ |

3 | Density | D = Mass/Volume | Kg/m³ |

4 | Speed | Acceleration | m/sec |

5 | Velocity | V = Displacement/Time | m/sec |

6 | Accessloration | A = Changing velocity/Time | m/sec² |

7 | Momentum | p = mv | Kg x m/sec |

8 | Impulse | I = FxΔt | Kg x m/sec |

9 | Force | F = ma | Kg x m/sec² |

10 | Work | W = FxS | N x M |

11 | Energy | E = Work Done | Joule |

12 | Power | P = Work/Time | Watt |

13 | Pressure | P = F/A | Pascal |

14 | Tension | Type of Force | Newton |

15 | Surface Tension | T = F/L | N/M |

16 | Stress | Type of Pressure | Pascal |

17 | Strain | Speed = Distance/Time | Unitless |

18 | Time Period | Time taken in a cycle | Sec |

19 | Frequency | F = 1/S | Hertz |

## Symbols

Alpha | α |

Bita | β |

Gama | γ |

Theta | θ |

psi | ψ |

Phi | Φ |

Nita | ŋ |

Kai | ϗ |

Omega | Ω |

Torque | τ |

Rou | ϱ |

Mue | µ |

Sigma | Σ |

Delta | Δ |

Epsilon not | ε |

Epsailon not | ε_{0} |

## What is Dimension Formula?

A Method to represent the quantity in the symbolic form of fundamental Quantities. [M L T]

## Dimension Formula

S.N | Quantity | Formula | Unit | Dimension |

1 | Mass | – | Kg | M`¹` |

2 | Length | – | Meter | L`¹` |

3 | Time | – | Second | T`¹` |

4 | Area | LxB | Meter² | L² |

5 | Volume | LxBxH | Meter`³` | L`³` |

6 | Speed | Distance/Time | m/sec | L`¹` T`⁻¹` |

7 | Velocity | Displacement/Time | m/sec | L`¹` T`⁻¹` |

8 | Accessloration | Velocity/Time | m/sec² | L`¹` T`⁻` ² |

9 | Density | mass/volume | kg/m`³` | M`¹` L`³` |

10 | Momentum | MxV | Kgxm/sec | M`¹` L`¹` T`⁻¹` |

11 | Force | Ma | Kgxm/sec² | M`¹` L`¹` T`⁻` ² |

12 | Type of force | Impulse | Kgxm/sec | M`¹` L`¹` T`⁻¹` |

13 | Work | FxS | Kgxm²/sec² | M`¹` L`²` T`⁻²` |

14 | Energy | Work Done | Joule | M`¹` L`²` T`⁻²` |

15 | Power | Work/Time | Joule/Sec | M`¹` L`²` T`⁻³` |

16 | Pressure | Forse/Area | Newton/m² | M`¹` L`⁻¹` T`⁻²` |

17 | Tension | Type of forse | Newton | Type of force |

18 | Surface Tension | Force/Length | N/m | M`¹` L`⁻²` T`⁻²` |

19 | Stress | Type of pressure | Newton/m² | M`¹` L`⁻¹` T`⁻²` |

20 | Strain | Change in shape/Original Shape | Unitless | 0 |

21 | Time Period | Time is taken in the cycle | Sec | T`¹` |

22 | Frequency | 1 | Hertz | T`⁻¹` |

23 | Angular Displacement | theta | radian | Dimension less |

24 | Angular Velocity | Displacement/Time | radian/sec | L`¹` T`⁻¹` |

## Application of Dimension

Convert one System into Another System

Q = n₁u₁ = n₂u₂

n₁[M₁ T₁ L₁] = n₂[M₂ L₂ T₂}

n₂ = n₁ [M₁ T₁ L₁]/[M₂ L₂ T₂]

## How many dyne in 1 Newton?

MKS to CGS

```
M₁ = Kg M₂ = Gram
L₁ = meter L₂ = Centimeter
S₁ = second S₂ = Seond
Dimension = M¹ L¹ T⁻²
n₂ = n₁ [M₁ T₁ L₁]/[M₂ L₂ T₂]
n₂ = (1) [Kg/Gram]¹ [Meter/centimeter]¹ [time/time]⁻²
n₂ = (1) [1000gram/gram]¹ [100centimeter/centimeter]¹ [1]⁻²
n₂ = 10⁵
```

## 2nd Application of Dimension

Check the characters of the formula

```
F = Mv²/r
Dimension of LHS [M¹ L¹ T⁻²]
Dimension of RHS [M¹] [L¹ T⁻¹]²/[L¹]
[M¹ L¹ T⁻²]
LHS = RHS
```

## Limitaion of Dimensions

- Dimensions don’t explain the nature of dimiensonal constant K.
- Dimensions are not used to form a relation between four independence.