📘 Chapter 1: Units and Dimensions

📘 Chapter 1: Units and Dimensions — Lecture 1

🔹 Physical Quantities kya hoti hain?

Physical quantities वो quantities होती हैं जिनको हम measure कर सकते हैं — जैसे length, mass, time, temperature, current, etc.
👉 These are measurable quantities in physics.

🔹 Types of Physical Quantities

1. Fundamental Quantities
ये वो quantities हैं जो independent होती हैं और जिन्हें किसी और quantity की मदद से define नहीं किया जा सकता।
🔹 Examples: Length (meter), Mass (kg), Time (second), Temperature (kelvin), Electric Current (ampere), Luminous Intensity (candela), Amount of Substance (mole)

2. Derived Quantities
Ye quantities fundamental quantities se milkar banti hain.
🔹 Examples: Speed = Distance/Time, Area = Length × Length, Volume = Length³

🔹 Unit kya hoti hai?

Unit ka matlab hota hai — standard reference jiski madad se hum kisi physical quantity ko measure karte hain.
👉 For example: Agar aap bolte ho ki "5 meter", to "5" hai numerical value aur "meter" hai unit.

🔹 Types of Units

1. Fundamental Units
Ye wahi units hain jo fundamental quantities ko measure karti hain.
🔸 Example: Meter (length), Second (time), Kilogram (mass)

2. Derived Units
Ye units derived quantities ke liye use hoti hain.
🔸 Example: m/s (speed), m² (area), kg·m/s² (force = Newton)

🔹 System of Units

Physics mein kuch standard systems of units follow kiye jaate hain:

1. CGS System – Centimeter, Gram, Second

2. FPS System – Foot, Pound, Second

3. MKS System – Meter, Kilogram, Second

4. SI System (International System of Units) – Sabse widely used system

🔹 Dimensions kya hoti hain?

Dimensions batati hain ki koi physical quantity kis kis fundamental quantity par depend karti hai.
👉 Example: Speed = Distance / Time
So, Dimensions of speed = [L][T⁻¹]

Quantity	Dimensions
Length	[L]
Mass	[M]
Time	[T]
Current	[A]
Temperature	[K]
Amount of substance	[mol]
Luminous intensity	[cd]

🔹 Dimensional Formula kya hoti hai?

Dimensional formula ek physical quantity ka algebraic expression hota hai in terms of basic dimensions.
👉 Example:

· Force = Mass × Acceleration = M × (L/T²) → [M¹L¹T⁻²]

📘 Chapter 1: Units and Dimensions — Lecture 1