**Chapter 1: The Science of Physics** Physics 1-2 Mr. Chumbley

**Section 1: What is Physics?**

**The Topics of Physics** • The origin of the word physics comes from the ancient Greek word phusika meaning “natural things” • The types of fields of physics vary from the very small to the very large • While some physics principles often seem removed from daily life, those same laws those same laws describe everyday events as well

**Areas of Physics**

**What is Physics?** • How can physics be defined if it so many different things? • Physics can be defined as: • The study of matter, energy, and the interactions between them • This definition is basic yet very broad

**The Scientific Method** • All scientific studies begin with a question • There is no single procedure all scientists follow • The scientific method is a set of steps that is common to most high quality scientific investigations

**Using Models to Describe Phenomena** • The physical world is very complex • In order to simplify the world, physicists construct models to isolate and explain the most fundamental aspects of a phenomenon • A model is a pattern, plan or description designed to show the structure or workings of an object, system, or concept • Models come in a variety of forms

**Using Models to Describe Phenomena** • In order to simplify the model, only the relevant components are considered part of the system • A system is a set of particles or interacting components considered to be a distinct physical entity for the purpose of study • Components not considered part of the system can generally be considered to have little to no impact on the model

**Models and Experimentation** • Models are extremely beneficial in helping to design experiments • Once a phenomenon has been identified, a hypothesis can be formed • A hypothesis is an explanation that is based on prior scientific research or observations and that can be tested • By creating a model of the phenomenon, the necessary factors for designing an experiment can be identified

**Models and Experimentation** • A model helps to ensure that controlled experiments are set up • A controlled experiment is an experiment that tests only one factor at a time by using a comparison of a control group with an experimental group

**Models and Predictions** • Once a model has been tested and supported repeatedly, that model can then be used to make predictions of future events • The best scientific models are used to predict outcomes in different scenarios that are different than the initial system

**Homework** • Read Chapter 1, Section 1: What is Physics? • Answer #1-5 of the Formative Assessment Questions on p. 9

**Section 2: Measurements in Experiments**

**What Can a Measurement Tell You?** • Often times we look at measurements as simple values, yet these values are different than simple numbers • A measurement tells dimension, the kind of physical quantity • A measurement tell the magnitude of the physical quantity • A measurement tells the unit by which the physical quantity is expressed

**Standard System of Measurement** • In 1960, an international committee agreed upon the Système International d’Unités (SI) for scientific measurements • The most common basic units of measure are:

**Standard System of Measurement** • Not every dimension can be described using just one of these units • Derived units are formed when units are combined with multiplication and division • Units help to identify the type of quantity being observed or measured

**SI Prefixes** Smaller than base unit Larger than base unit

**Using SI Prefixes** • The advantage of using SI and its prefixes is that it can put numbers into understandable values • Converting between one unit to another is simply a matter of moving the decimal

**SI Conversions** • To convert between one unit and another we use a conversion factor • Conversion factors are built from any equivalent relationship • The value of a conversion factor is always equal to 1 • Desired unit for conversion is opposite the location of the original unit

**SI Conversions** • Example #1: Convert 37.2 mm to m. Conversion factor for mm to m is:

**Scientific Notation** • Scientific notation is a way of expressing numbers consistently • The format for scientific notation is a value, called the significand, that is expressed as a value with a single digit left of the decimal point multiplied by a power of 10 • For example

**Practice!** • Find a partner nearby • Complete the Practice problems on page 15, #1-5

**Homework** • Chapter 1 Review p. 27-28 • Complete # 5, 8, 10, 11, 12, 13

**Accuracy and Precision** Accuracy Precision • A description of how close a measurement is to the correct or accepted value of the quantity measured • The degree of exactness of a measurement

**Uncertainty and Error** • Uncertainty is the measure of confidence in a measurement or result • Uncertainty can arise from a variety of sources of error • Method error occurs when measurements are made using inconsistent instruments, techniques, or procedures • Instrument error occurs when the tools used to take measurements have flaws

**Precision and Instruments** • The exactness of a measurement is often times dependant upon the tool used • When taking measurements with a tool, the precision of that tool is the smallest marked measurement • Precision can often times be improved by making an estimation of one additional digit • While an estimated digit carries a level of uncertainty, it still provides greater precision

**Significant Figures** • One way we indicate precision in measurement is through significant figures • Significant figures are those digits in a measurement that are known with certainty plus the first digit that is uncertain

**Significant Figures and Scientific Notation** • When the last digit in a measurement is zero, there can be confusion concerning the value • In this situation, using scientific notation can add additional clarity since scientific notation includes all significant figures

**Rules for Determining Significant Figures (Figure 2.9 on** page 18)

**Rules for Calculating with Significant Figures (Figure 2.10** on page 19)

**Calculators and Calculations** • Calculators do not take into account significant figures • While the calculator can give you the value of a calculation, determining the number of significant figures is done manually • When rounding occurs multiple times within a calculation, there can be significant error • Generally, it is better to carry extra non-significant digits in calculations and round the answer to the appropriate number of significant digits at the very end

**Rules for Rounding in Calculations(Figure 2.11 on page 20)**

**Homework** • Section 2: Formative Assessment (p 20) • #3 and #4 • Chapter 1 Review (p 28) • #16, 20, 22

**Section 3: The Language of Physics**

**Mathematics and Physics** • In physics, the tools of mathematics is used to analyze and summarize observations • This can be in a variety of forms, most commonly tables, graphs, and equations

**Tables** Data Table: Time and Distance of Dropped-Ball Experiment • Tables are a convenient way to organize data • Having data organized in a table allows for easier use for comparison or calculation • All tables and data should be clearly and appropriately labeled

**Graphs** • Constructing graphs can help to identify relationships or patterns • The relationships described in graphs can often times be put into equations

**Equations** • In mathematics equations are used to describe relationships between variables • In physics, equations serve as tools to describe the measurable relationships between physical quantities in a situation

**Equations and Variables** • Generally, scientists strive to make equations as simple as possible • To do this scientists use different operators and variables in place of words:

**Dimensional Analysis** • Dimensional analysis is a procedure that can be used to determine the validity of equations • Since equations treat measurable dimensions as algebraic quantities, mathematical manipulations can be performed

**Order of Magnitude** • Dimensional analysis can also be used to check answers • Using basic estimation to a power of 10, simple calculations can be made to determine the relative scale of the answer

**Derived Units with Dimensional Analysis** • Similar to converting between base units in SI, conversions of derived units is sometimes necessary • When this happens, each portion of the derived unit needs to be converted