Objectives

1. Chapter 1 Section 1 What Is Physics? Objectives • IdentifyPhysics and describe theactivities and fields that involve the major areas within physics. • Describethe processes of the scientific method. • Describehow a controlled experiment can be used to test a hypothesis.

2. Chapter 1 Section 1 What Is Physics?

3. Chapter 1 Section 1 What Is Physics? Physics • Physicsis a branch of science that involves the study of the physical world around us. • Attempts to describe nature in an objective way through measurements. • The goal of physicsis to use a small number of basic concepts, equations,and assumptions to describe the physical world. • Physics principles can then be used to makepredictions about the world we live in.

4. Chapter 1 Section 1 What Is Physics? The 7 Branches of Physics • Mechanics -study of motion and its causes and the interactions between objects -ex. falling objects, friction, weight, spinning objects • Thermodynamics -study of heat and temperature -ex. objects melting and freezing, cooling engines and machinery, refrigeration

5. Chapter 1 Section 1 What Is Physics? • Vibrations and Waves -study of specific types of repetitive motions -ex. sound, springs, and pendulums • Optics -study of light -ex. mirrors, lenses, color, and astronomy • Electromagnetism -study of electricity, magnetism, and light -ex. electrical charges, circuitry, and magnets

6. Chapter 1 Section 1 What Is Physics? • Relativity -the study of particles moving at any speed, especially very high speeds -ex. particle collisions, particle accelerators, and nuclear energy • Quantum Mechanics -the behavior of subatomic particles -ex. the atom and its parts

7. Chapter 1 Section 1 What Is Physics? Physics and Technology

8. Chapter 1 Section 1 What Is Physics? The Scientific Method • There is no single procedure that scientists follow in their work. However, there are certain steps common to all good scientific investigations. • These steps are called thescientific method.

9. Chapter 1 Section 1 What Is Physics? Steps of the Scientific Method: • Make observations and collect data that lead to a question. • Form a hypothesis and test it using a controlled experiment. • Interpret results and analyze data. 4. State a conclusion.

10. Chapter 1 Section 1 What Is Physics? Hypotheses • Ahypothesisis an educated guess that is based on prior scientific research or observations and that can be tested. • The process of simplifying and modeling a situation can help you determine the relevant variables and identify a hypothesis for testing.

11. Chapter 1 Section 1 What Is Physics? Galileo’s Hypotheses • Before Galileo, scientists believed heavy objects fell more rapidly than light objects. • Galileo considered the situation shown. • If the heavy brick falls faster, what would happen if they were tied together?

12. Chapter 1 Section 1 What Is Physics? Galileo’s Hypothesis • Since the two bricks can’t fall faster and slower than the heavy brick, Galileo concluded the original hypothesis was wrong. • Galileo’s hypothesis: • All objects fall at the same rate in the absence of air resistance.

13. Chapter 1 Section 1 What Is Physics? Controlled Experiments -A hypothesis must be tested in acontrolled experiment. -In a controlled experiment, only one factor is changed, all other factors remain the same and are called constants. -Any one factor that can be changed is called a variable. -A controlled experiment tests only one factor at a time by using a comparison of acontrol groupwith an experimental group.

14. Section 2 Measurements in Experiments Chapter 1 Objectives • Listbasic SI units and the quantities they describe. • Convertmeasurements into scientific notation. • Distinguishbetween accuracy and precision. • Usesignificant figures in measurements and calculations.

15. Section 2 Measurements in Experiments Chapter 1 • Dimension - the kind of physical quantity being measured • Examples: length, mass, volume, time, and so on • Each single dimension is measured in specific units. • meters, grams, liters, seconds, and so on • The derived units are combinations of other units. • m/s, km/hr/s, kg*m/s, and many others • Scientists use the SI System of Measurement. • Also known as the Metric System. Measurements

16. Section 2 Measurements in Experiments Chapter 1 SI Prefixes In SI, units are combined withprefixesthat symbolize certainpowers of 10.The most common prefixes and their symbols are shown in the table.

17. Section 2 Measurements in Experiments Chapter 1 SI Unit Conversion A typical bacterium has a mass of about 2.0 fg. Express this measurement in terms of grams and kilograms. Given: mass = 2.0 fg Unknown: mass = ? g mass = ? kg

18. Section 2 Measurements in Experiments Chapter 1 Sample Problem, continued Build conversion factors from the relationships given in Table 3 of the textbook. Two possibilities are: Only the first one will cancel the units of femtograms to give units of grams.

19. Section 2 Measurements in Experiments Chapter 1 Sample Problem, continued Take the previous answer, and use a similar process to cancel the units of grams to give units of kilograms.

20. Section 2 Measurements in Experiments Chapter 1 Unit Conversions • Convert the following: 1523 g to kg 1.523 kg 348 cm to m 3.48 cm 8.34 µm to m 0.00000834 m

21. Section 2 Measurements in Experiments Chapter 1 Accuracy and Precision • Accuracyis a description of how close a measurement is to the correct or accepted value of the quantity measured. • Precisionis the degree of exactness of a measurement. • A numeric measure of confidence in a measurement or result is known asuncertainty.A lower uncertainty indicates greater confidence.

22. Section 2 Measurements in Experiments Chapter 1 Accuracy and Precision

23. Section 2 Measurements in Experiments Chapter 1 Significant Figures • It is important to record theprecision of your measurementsso that other people can understand and interpret your results. • A common convention used in science to indicate precision is known assignificant figures. • Significant figuresare those digits in a measurement that are known with certainty plus the first digit that is uncertain.

24. Section 2 Measurements in Experiments Chapter 1 Always significant: Nonzero digits and zeros between them: 357 has 3 significant figures 3075 has 4 significant figures Zeros to the right of a non-zero digit, and right or left of a written decimal point: 57.00 has 4 significant figures 2.000 000 has 7 significant figures

25. Section 2 Measurements in Experiments Chapter 1 Never Significant: Zeros to the right of a non-zero digit, and left of an unwritten decimal point: 100 has only 1 significant figures 25000 has only 2 significant figures Zeros to the right or left of the decimal point in numbers less than one: 0.892 has only 3 significant figures 0.00046 has only 2 significant figures

26. Section 2 Measurements in Experiments Chapter 1 Addition and Subtraction: The final digit should be in the same place as the leftmost uncertain digit. 213.67 437.234 - 98 +12.5 115.67 449.734 Since the 8 is the leftmost uncertain digit, the answer should be rounded to 116 Sincethe 5 is the leftmost uncertain digit, the answer should be rounded to 449.7

27. Section 2 Measurements in Experiments Chapter 1 Multiplication and Division Round off to the same number of significant figures as in the measurement with the fewest significant figures. 12 cm x 4.3 cm= 51.6 cm2 rounds to 52 cm2 2.50g / 0.04 cm3= 62.5 g/cm3 rounds to 60 g/cm3

28. Section 3 The Language of Physics Chapter 1 Objectives • Interpretdata in tables and graphs, and recognize equations that summarize data. • Distinguishbetween conventions for abbreviating units and quantities. • Usedimensional analysis to check the validity of equations. • Performorder-of-magnitude calculations.

29. Section 3 The Language of Physics Chapter 1 Tables -used to organize data into a clear and meaningful way A clear trend can be seen in the data. The more time that passes after each ball is dropped, the farther the ball falls.

30. Section 3 The Language of Physics Chapter 1 Graphs -mathematical, like from the previous table, can be used to create a graph The shape of the graph provides information about the relationship between time and distance.

31. Section 3 The Language of Physics Chapter 1 Equations • Show relationships between variables • Directly proportional • Inversely proportional • Inverse, square relationships • Describe the model in mathematical terms • Allow you to solve for unknown quantities

32. Section 3 The Language of Physics Chapter 1 Manipulating Equations Speed s = d t Force F = m x a

33. Section 3 The Language of Physics Chapter 1 Equation from Dropped-Ball Experiment • The Greek letterD(delta) means“change in.”The abbreviationDyindicates thevertical changeina ball’s position from its starting point, andDtindicates thetime elapsed. The 1/2a is the abbreviation for half of the acceleration due to gravity. • With symbols, the word equation above can be written as follows: Dy = 1/2a(Dt)2 • This equation allows you toreproduce the graphandmake predictionsabout the change in position for any time.