Unit 1: Physical Quantities and Measurement

Unit 1: Physical Quantities and Measurement

Introduction to Physics

• Definition: Measurements are essential in describing and understanding the physical world. Over centuries, methods have evolved for improved accuracy.

• Key Idea: Physics serves as a foundation for other sciences like biology and chemistry.

  • Example: Fluid movements in biology and subatomic particles in chemistry are grounded in physics.

• Role of Technology: Technologies such as computers, rockets, and PET scans are based on physics principles.

Branches of Physics

• Current Major Branches:

  • Mechanics

  • Optics

  • Oscillation and Waves

  • Thermodynamics

  • Electromagnetism

  • Astrophysics

  • Quantum Physics

  • Atomic Physics

  • Nuclear Physics

Physical vs. Non-Physical Quantities

• Physical Quantities: Measurable quantities such as length, mass, time, density, temperature.

• Non-Physical Quantities: Qualities that cannot be measured, e.g., taste, color, feelings.

Measurement Basics

• Definition: Measurement compares an unknown physical quantity to a standard.

• Unit: The standard used for comparison.

• Example: 1.65 meters (where 1.65 is the magnitude and meter is the unit).

Types of Physical Quantities

Base and Derived Quantities

• Base Quantities: Fundamental quantities (e.g., length, mass, time) that are defined and cannot be derived further.

• Derived Quantities: Quantities derived from base quantities (e.g., area, volume).

International System of Units (SI)

SI Base Units

• Base Quantities and Units:

  • Length: Meter (m)

  • Mass: Kilogram (kg)

  • Time: Second (s)

  • Electric Current: Ampere (A)

  • Temperature: Kelvin (K)

  • Amount of Substance: Mole (mol)

  • Light Intensity: Candela (cd)

Derived Units

• Examples of Derived Quantities:

  • Area: $m^2$

  • Volume: $m^3$

  • Speed: $m/s$

  • Acceleration: $m/s^2$

  • Force: $kg imes m/s^2$ = Newton (N)

  • Pressure: Pascal (Pa) = $kg/(m imes s^2)$

  • Energy: Joule (J) = $kg imes m^2/s^2$

Scientific Notation

• Definition: A compact way of expressing very large or small numbers using powers of ten.

• Format: $Number = Mantissa imes 10^{Exponent}$

• Examples:

  • Width of the universe: $8.8 imes 10^{26}$ m

  • Mass of earth: $5.98 imes 10^{24}$ kg

Prefixes to Power of Ten

• Purpose: Simplifies representation of very large or small measurements.

• Common Prefixes:

  • Kilo (k): $10^{3}$

  • Mega (M): $10^{6}$

  • Giga (G): $10^{9}$

  • Nano (n): $10^{-9}$

  • Pico (p): $10^{-12}$

  • Femto (f): $10^{-15}$

• HExamples:

  • Thickness of paper: $0.04$ mm = $4.0 imes 10^{-2}$ m

Scalars and Vectors

Scalar Quantities

• Definition: Physical quantities completely described by magnitude alone. Examples: distance, speed, time, mass.

Vector Quantities

• Definition: Require both magnitude and direction for full description. Examples: displacement, velocity, force, acceleration.

• Representation: Graphically using arrows (length = magnitude, direction = orientation).

Measuring Instruments

Types of Instruments

• Simple Instruments: Rulers, stopwatches.

• Complex Instruments: Atomic Force Microscope (AFM), Scanning Tunneling Microscope (STM).

Metre Rule and Measuring Tape

• Definition: Standard tools for measuring length with markings (divisions) for precision.

• Least Count: Minimum measurable value, typically assessed in mm on a metre rule.

Vernier Caliper

• Description: Instrument for measuring small dimensions (under 1 mm).

• Learnt Steps: Combining main and vernier scale readings for accurate measurement.

• Least Count Calculation: Determined using the smallest division scale divided by the total divisions on the vernier.

Digital Vernier Calipers

• Advantage: Higher precision with a least count of 0.01 mm.

Example Applications

• Calculating using Scientific Notation: Convert distances, masses, etc. to scientific notation and express using appropriate prefixes.