Chapter 1 Lecture Outline

Nature of Physics

• Definition: The most basic and fundamental science.

• Goal: To understand how everything works at its most fundamental level.

• Scope: Encompasses the study of the universe from the largest galaxies to the smallest subatomic particles.

• Focus: Describes the interactions of energy, matter, space, and time to uncover the fundamental mechanisms underlying various phenomena.

Topics Covered in PHYS 220 (Physics – I)

• Key Areas:

  • Mechanics

  • Fluid dynamics

  • Momentum and Impulse

  • Force: The cause of motion

  • Work, Energy, and Power

• Principles:

  • Pascal's law

  • Archimedes' principle

  • Continuity equation

  • Bernoulli's principle

• Applications:

  • Kinematic equations

  • Newton's three laws of motion

  • Conservation of momentum

• Types of Motion:

  • Linear motion

  • Rotational motion

Physical Quantities, Measurements, and Units

• Physical Quantity: A property that can be quantified by measurement (e.g., length, time, mass).

• Measurement: Comparing an unknown quantity with a known standard reference quantity.

• Units: Standards that represent physical quantities (e.g., meter for length).

Old System of Units

• Characteristics: Early units based on the human body.

• Current Usage: Only the US, Burma, and Liberia still use this system significantly.

• Challenges: Lack of consistency hinders commerce and scientific fields, leading to the need for a rational/common system of units.

Major Systems of Units

• British (English) System: Widely used in the US (e.g., foot, pounds).

• International System of Units (SI): Current international standard (Metric units) defined by MKS.

SI Units and Fundamental Quantities

• Fundamental Units: Seven dimensionally independent units:

  • Meter (m) - length

  • Kilogram (kg) - mass

  • Second (s) - time

  • Ampere (A) - electrical current

  • Kelvin (K) - temperature

  • Mole (mol) - amount of substance

  • Candela (cd) - luminous intensity.

Measurement of Length

• Old Reference: Based on the distance between the North Pole and the Equator.

• New Reference: Based on the distance light travels in a vacuum during 1/299,792,458 of a second.

Measurement of Mass

• Definition: Quantity of matter.

• SI Unit: Kilogram (kg) defined by the fixed numerical value of the Planck constant.

Measurement of Time

• Definition: Continuous forward flow of events; only moves in one direction.

• SI Unit: Second (s) based on atomic clock (Cs133 atom) vibrations.

Derived Units

• Usage: Combines fundamental units for convenience.

• Examples of Derived Units:

  • Newton (N) = kg·m/s²

  • Joule (J) = kg·m²/s²

  • Watt (W) = kg·m²/s³

Scientific Notation and SI Prefixes

• Purpose: Conveniently expressing very large or small numbers.

• SI System: Based on powers of ten; different prefixes denote different powers.

• Examples: 1,000,000 = 10⁶; 0.000001 = 10⁻⁶.

Rules for Scientific Notation

• Exponent increases by one for each decimal place shifted left; decreases for right.

  • Example: 360,000 = 3.6×10⁵.

Conversion of Units

• Method: Multiply the quantity by a fraction equal to 1 defined by the conversion factor.

• Example: Convert 316 ft² to m² using conversion factors to find 29.35 m².

Significant Figures

• Importance of precision in measurements; reflects the accuracy of measured values.

• Examples:

  • 4.6000 (5 SF)

  • 0.0002 (1 SF)

Rules for Significant Figures

1. Non-zero numbers are significant.

2. Zeros between non-zero numbers are significant.

3. Leading zeros are not significant.

4. Trailing zeros after a decimal are significant—whole numbers with no decimal are not.

5. Including a decimal makes trailing zeros significant.

Processing Significant Figures

• Each of the significant figures is expressed accurately while rounding in calculations.

Error and Uncertainty in Measurement

• All measurements involve error and uncertainty; factors include calibration issues, physical variations, instrument resolution, and human error.

Example Calculations for Uncertainty

• Example 1: Percent uncertainty of a 5-lb bag of apples measured at 5.1 ± 0.1 lb is approximately 2%.

Error Analysis

• Percentage Error Formula:

  • % Error = (Your Result - Accepted Value) / Accepted Value × 100.

• Percentage Difference: Used when comparing results from different methods.

Error Propagation

• Rule for combined measurement errors:

  • % Error in R = |n1| %x1 + |n2| %x2 + ... where ni is the power in the calculation.

Order of Magnitude Estimation

• Provides a rough idea of the magnitude of a quantity, helpful for verification of computations.