Honors Physics Notes - Unit 0: Basic Science

Course Setup and Welcome

  • Pick up safety sheet handout on front counter
  • Find a seat (sit where you can clearly see the text on the screen)
  • Complete the student information Google form: https://forms.gle/WX3ydNp4iUSUjuFi9
  • The above form is also linked on Canvas
  • Welcome to Honors Physics

My Background

  • From Mauldin, SC
  • South Carolina
  • *

College

  • Materials Science and Engineering degree from NC State University
  • N

Work Experience

  • Worked as a process engineer in research and development at Micron Technology in Boise, Idaho
  • W
  • EMO
  • PRI

Teaching Experience

  • Four years teaching in Virginia
  • Ten years teaching in NC

Syllabus

  • Posted on Canvas

What is Science? Underlying Assumptions

  • The word science comes from the Latin word scientia meaning “Knowledge”
  • Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe
  • Underlying Assumption: The natural world is understandable through careful collection and critical analysis of evidence
  • Every branch of modern science has developed its principles and explanations with this assumption

What is Physics?

  • Physics is the study of the physical world: energy, matter, and how they are related
  • Quote: "Physics is the only real science. The rest are just stamp collecting." — Ernest Rutherford

Introductory Resources for Physics

  • Prof. Dave – Intro to Classical Physics (link)
  • Domain of Science - map of physics (link)
  • Khutoryansky - Philosophy of Physics (link)
  • What is physics?

Scales and Domain of Physics

  • Far larger than 10^{-9} ext{ m}
  • Near or less than 10^{-9} ext{ m}
  • Far less than 3\times 10^{8} ext{ m/s} (speed)
  • Classical Mechanics
  • Quantum Mechanics
  • Relativistic Mechanics
  • Quantum Field Theory

Major Fields and Topics in Physics (Overview)

  • Classical Physics
  • Quantum Physics
  • Relativity
  • Gravitation
  • Optics (Reflection, Refraction, Diffraction, Telescopes, Microscopes)
  • Waves (Wave phenomena)
  • Modern Physics (Statistics, Thermodynamics, Nuclear Physics, Condensed Matter, Quantum Information, Particle Physics, etc.)
  • Subfields listed in the slide: CALCULUS, FIELDS, ELECTROMAGNETISM, NUCLEAR PHYSICS, FUSION, LASERS, ENTROPY, DARK MATTER, etc.
  • Note: This is a representative map of physics domains and not an exhaustive syllabus.

Why Take Physics?

  1. To understand the physical world
  2. You have to (learn the methods and tools)
  3. If you’re good at this and like this, there are excellent career opportunities

Highest Starting Pay by Major (Sample Data)

  • Chemical engineering — \$80{,}000
  • Computer engineering — \$78{,}000
  • Computer science — \$76{,}000
  • Electrical engineering — \$75{,}000
  • Aerospace engineering — \$71{,}000
  • Industrial engineering — \$70{,}000
  • Mechanical engineering — \$70{,}000
  • Civil engineering; Construction services; Economics; Finance; General engineering; Miscellaneous engineering; Physics (listed among majors; exact value not shown in the provided data)

Scientific Method

  • Scientific Method (overview): a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge
  • Steps (in order):
    • Observation
    • Question
    • Research
    • Hypothesis
    • Experiment
    • Analysis
    • Draw Conclusions
    • Scientific Law and Theory
  • Scientific Method (label): Scientific Method

Observation, Question, Research

  • Observation: Objects tend to fall to the ground
  • Question: How does mass affect the rate at which an object falls?
  • Research: Internet, textbooks, library, expert, etc.; Observe, Question, & Research

Hypothesis

  • Example: Heavier objects fall faster than lighter ones
  • The hypothesis must be falsifiable: a statement that can be tested and proven wrong
  • Example of non-falsifiable: "there is a teapot orbiting Earth" (not falsifiable because there’s no definitive way to prove it doesn’t exist)
  • Hypothesis

Prediction, Experiment, Conclusion

  • Prediction: Heavy ball will fall faster than lighter ball and hit the ground first
  • Experiment: Drop a heavy ball and a light ball at the same time and observe which hits first
  • Must be reproducible for others to verify
  • Prediction & Experiment
  • Conclusion: If the prediction was incorrect, evaluate the experiment setup and consider a new hypothesis
  • Conclusion

Scientific Law vs Scientific Theory

  • Scientific Law: a rule of nature that sums up related observations to describe a pattern in nature; answers “what” will happen
  • Scientific Theory: an explanation based on many observations supported by experimental results; answers “why” things work as they do
  • Both require extensive testing and can change with new falsifying evidence
  • Scientific Law and Theory

History of the Law of Falling Objects

  • Aristotle proposed that more massive objects fall faster
  • Galileo showed that falling speed depends on air resistance and time of fall, not mass
  • Apollo astronauts tested this on the Moon in 1971 (vacuum, no air resistance)
  • Revision and Further Testing links (Moon, Vacuum Chamber)

Theory of Falling Objects

  • Aristotle: objects fall because they seek their natural places
  • Newton: objects fall due to a force of attraction between masses; all objects with mass have this force of attraction
  • Einstein: attraction between masses is due to spacetime curvature caused by mass
  • Revision

Closure and Administrative Tasks

  • Get Safety Sheets signed and returned by Monday
  • Complete Canvas assignment: Hampton Syllabus Quiz
  • Advisory Period, Split Lunch, Bell Schedule
  • Mathematics and Science timetable notes (84 min periods, etc.)

Before Class and Materials

  • Pick up handout on front left counter
  • Take out signed safety contracts
  • You’ll need a calculator today before class

Scientific Notation and Scientific Measurements

  • Scientific measurements are often very small or very large; scientific notation is commonly used
  • Placing numbers into scientific notation:
    • Place a decimal after the first nonzero digit from the left side of the number
    • Only keep zeros if they were significant in the original value
    • The exponent (of 10) equals the number of digits the decimal moved past
    • The sign of the exponent is positive for numbers greater than 1 and negative for numbers less than 1
  • Scientific notation examples: 34500, 0.00121, 3.45 \times 10^{4}, 1.21 \times 10^{-3}, 3.45\text{E}4, 1.21\text{E}-3

Reverting from Scientific Notation

  • If the number needs to be taken out of scientific notation form, move the decimal the same number of places as the exponent
  • Remember:
    • Negative exponent means number is less than 1
    • Positive exponent means number is greater than 1
  • Reverted examples: 4.12 \times 10^{3} → 4120; 8.1 \times 10^{-4} → 0.00081

Operations with Scientific Notation

  • Multiplication: multiply the numbers, add the exponents
  • Division: divide the numbers, subtract the exponents
  • Addition/Subtraction: must have a common exponent; add/subtract the numbers without changing the exponents
  • Math with Scientific Notation

Calculator Tips with Scientific Notation

  • USE A CALCULATOR!
  • When performing operations with scientific notations, place the entire scientific notation number in parentheses or use the EE function to avoid mistakes
  • My Scientific Notation Recommendation

Measurements and SI Units

  • Measurement: a comparison between an unknown quantity and a standard; has a numerical value and a unit
  • The unit is the standard
  • Measurements quantify observations
  • The meter is defined as the length of the path traveled by light in vacuum during a time interval of \frac{1}{299{,}792{,}458}\ \text{s}
  • International System of Units (SI): modern form of the metric system; SI base units are the basic set of units from which all other SI units can be derived
  • SI Units

Significant Figures (Sig Figs)

  • The significant figures in a measurement include all digits that are known, plus a last digit that is estimated
  • Rules for significant figures:
    1) Nonzero digits are significant: 4.51 has 3 sig figs
    2) Leading zeros are never significant: 0.0071 has 2 sig figs
    3) Imbedded zeros are significant: 708.01 has 5 sig figs
    4) Trailing zeros are significant only if a decimal is present: 5000 has 1 sig fig; 9.10 has 3 sig figs; 5000. has 4 sig figs
    5) In scientific notation, all digits before the × are significant: 4.0\times 10^{8} has 2 sig figs
  • Some numbers have an infinite number of significant figures (exact values): counted items (e.g., 19 students), mathematical definitions (e.g., 1 foot = 12 inches exactly), numbers spelled out in words (e.g., two liters is exactly two liters)
  • Exact Values

Rounding Numbers (Sig Figs)

  • Rules for rounding: round to three sig figs in this class
  • 5 or higher rounds up; 4525 → 4530
  • Less than 5 rounds down; 0.17448 → 0.174
  • There are rules to rounding answers to the correct number of significant digits; in this class, round everything to 3 sig figs for ~97% of questions
  • Significant Figures in Calculations

Practice with Sig Figs (Kahoot)

  • Kahoot - Measuring with sig figs
  • Kahoot: Taking measurements (link)

Measurements Practice and Timings

  • Closure: Yesterday's Canvas syllabus assignment due today
  • Science Math quiz on Friday!

Before Class Preparations

  • Pick up two worksheets on side table

Treat Units Like Variables (Examples)

  • 4 m – 2 m = ??
  • 4 m * 2 m = ??
  • 4 m + 2 g = ??
  • 4 m * 2 g = ??
  • 9 cm^3 / 3 cm = ??
  • 2 hr * 40 mi/hr = ??

Conversion Factors

  • When you write one part of an equality in the numerator and the other in the denominator, it is called a conversion factor. Every equality can make two conversion factors.
  • Examples:
    • 100\ cm = 1\ m or 1\ m = 100\ cm
    • 1.0\ kg = 1\text{ (unitless)} = 2.2\ lbm
    • 1.0\ N = 4.5\ lbf
    • 1.0\ mile = 1.6\ km
    • 1.0\ m/s = 2.2\ mph
    • 1.00\ year = 365.25\ days

Steps for Dimensional Analysis

1) Write the value given in the problem with units
2) Cross-cancel units of the given value until you are left with the new units
3) Plug in numbers from the conversion factor
4) Multiply the numbers in the numerator and divide by numbers in the denominator
5) Check units and significant figures

Example: Convert 5.0 km to miles

  • Given: 5.0\ \text{km}
  • Use factor: \frac{1.0\ \text{mile}}{1.6\ \text{km}}
  • Calculation: 5.0\ \text{km} \times \frac{1.0\ \text{mile}}{1.6\ \text{km}} = 3.1\ \text{miles}

Metric Prefixes (Power of 10)

  • Prefix Symbol Notation
  • tera T 10^{12}
  • giga G 10^{9}
  • mega M 10^{6}
  • kilo k 10^{3}
  • deci d 10^{-1}
  • centi c 10^{-2}
  • milli m 10^{-3}
  • micro \mu 10^{-6}
  • nano n 10^{-9}
  • pico p 10^{-12}

Useful Conversion Factors to Know

  • 1.0\ \text{kg} = 2.2\ \text{lbm}
  • 1.0\ \text{N} = 4.5\ \text{lbf}
  • 1.0\ \text{mile} = 1.6\ \text{km}
  • 1.0\ \text{m/s} = 2.2\ \text{mph}
  • 1.00\ \text{year} = 365.25\ \text{days}

Dimensional Analysis Practice

  • Solve the following using dimensional analysis (recall sig figs):
    • Change 6.23\ \text{m/s} to mph
    • Change 120\ \text{kg} to lbm
  • (Examples are shown in the unit plan and practice sheets.)

Let the Units Be Your Guide (Compound Units)

  • Compound units have multiple dimensions, e.g., mph (miles per hour) or density (g/L)
  • Both numerator and denominator units can be changed
  • Dimensional analysis should be used and let the units guide problem solving
  • Compound Units

Compound Units Examples

  • Change 768\ \text{mi}/\text{hr} to \text{m}/\text{s}
  • Convert 9.82\ \text{kg}\cdot \text{s} to \text{m}^2
  • Convert 8.1\times 10^{-4} to a form with different unit scales (example provided in slides)

Lab Question Form (General Form)

  • General Form of Lab Question: How does [independent variable] affect [dependent variable]

Identifying Variables (DRY MIX Trick)

  • A variable is any factor that might affect the behavior of an experiment
  • Independent variable: factor that is changed or manipulated during the experiment; Plotted on the x-axis
  • Dependent variable: factor that depends on the independent variable; Plotted on the y-axis
  • DRY MIX trick:
    • D - Dependent
    • R - Response
    • Y-AXIS
    • M - Manipulate
    • I - Independent
    • X - AXIS

Line of Best Fit and Linear Relationships

  • You have a scatter plot; line of best fit describes the relationship shown in the graph
  • Use the line to make more accurate predictions
  • Draw a line that best fits your data
  • Linear relationship: y = mx + b
    • m = slope (rise over run)
    • b = y-intercept (value when x = 0)
  • To write the physics equation for the line, pick two points on your line of best fit

Ball Bouncing Activity (Example Lab)

  • Question: How does the height of drop affect the height of the rebound?
  • Identify:
    • Independent variable: initial drop height
    • Dependent variable: rebound height
  • Create a data table and graph:
    • Draw axes far from paper edges
    • Label axes with variable names and units
    • Draw a best-fit line
    • Determine slope of the best-fit line and the y-intercept
    • Write the physics equation for the line
  • Analysis: What does the slope mean? What does the y-intercept mean?
  • Activity: Ball Bouncing Activity

Closure

  • Finish up graphs

Administrative and Scheduling Notes (Summary)

  • Before Class: Pick up two worksheets on side table; you will need a calculator today
  • Closure items include(Canvas) syllabus quiz and advisory schedules
  • Graphing and data analysis tasks are part of the course activities