Physics: Units and Measurement Basics

Jul 5, 2024

Physics Unit and Measurement

Introduction

  • Chapter: 21 (Unit and Measurement)
  • Main Topic: Units and Measurement
  • Important Points: Dimensions (time, fundamental metrics, etc.)

Important Points

  • Best Notes: Are those that you create with love
  • Website: PDFs of lectures will be available on Wi-Fi Panday
  • Daily Practice Problem: 10 questions, to be downloaded from the site

Story: Richard and the Chess Board

  • Scientist: Richard data exchange (e.g., chess board pieces and game)
  • Players: Sushma and Pushpa
  • Key Point: Scientific methods and reasoning

Physical Quantity and Its Types

Physical Quantity

  • Division: Basic laws and physical laws
  • Primary metrics: Length, mass, time, temperature, etc., are measured in measurements
  • Main Types:
    • Fundamental Units: Meter (length), kilogram (mass), second (time), kelvin (temperature), ampere (electric current), candela (luminous intensity), mole (amount of substance)
    • Derived Units: Area, volume, velocity, acceleration, etc.
    • Supplementary Units: Angle, solid angle

Fundamental Measurement Units

  • Length: Meter (m)
  • Mass: Kilogram (kg)
  • Time: Second (s)
  • Temperature: Kelvin (K)
  • Electric Current: Ampere (A)
  • Luminous Intensity: Candela (cd)
  • Amount of Substance: Mole (mol)

Derived Units

  • Area: Square meter (m²)
  • Volume: Cubic meter (m³)
  • Velocity: Meter per second (m/s)
  • Acceleration: Meter per second² (m/s²)
  • Force: Newton (N): kg·m/s²
  • Energy: Joule (J): N·m
  • Pressure: Pascal (Pa): N/m²

Dimensions

  • Definition: The expression of the measurement of any physical quantity
  • Main Dimensions: Length (L), Mass (M), Time (T), Temperature (θ), Electric Current (I), Luminous Intensity (J), Amount of Substance (N)
  • Dimensional Formula:
    • e.g.: Force (F)= [MLT^-2]
    • Energy (E): [ML²T^-2]

Physical Quantity Expressions and Unit Examples

  • Velocity: [L]/[T] = m/s
  • Acceleration: [L]/[T²] = m/s²
  • Force: [M][L][T^-2] = kg·m/s²
  • Energy: [M][L²][T^-2] = kg·m²/s²
  • Pressure: [M][L^-1][T^-2] = kg/(m·s²)

Units and Their Utility

  • Objective: To help measure, compare and formulate rules for physical quantities
  • Measurement Systems: SI unit system is the most popular
  • Special Points: Some units do not have a dimensional expression (like supplementary units)

Specific Concepts and Examples

  • Regular Quantities: Physical quantities based on standards
  • Miscellaneous: Examples, formulas, and equations (based on the given measurement system)

Conclusion

  • It's essential to understand every fundamental unit for comprehensive study
  • Understanding physical quantities and their units will help students in further progress