Chapter 1: The Science of Physics

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

2. Section 1: What is Physics?

3. 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

4. Areas of Physics

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

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

13. Section 2: Measurements in Experiments

14. 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

15. 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:

16. 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

17. SI Prefixes Smaller than base unit Larger than base unit

18. 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

19. 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

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

21. 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

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

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

24. 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

25. 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

26. 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

27. 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

28. 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

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

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

31. 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

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

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

34. Section 3: The Language of Physics

35. 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

36. 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

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

38. 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

39. 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:

40. 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

41. 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

42. 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