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)

Fundamental Quantities units

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

SI System

Supplementary:-

Quantity	Formula	Unit
2D Angle	θ = Arc/Radius	Radian
3D Angle	–	Steradian

Supplementary SI Unit

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

Derived Quantity

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	ε₀

Important Symbols

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`

Dimension formula

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.