ch 1 Holt physics for science and agriculture

ch 1 Holt physics for science and agriculture

1. The Science of Physics Chapter 1 Table of Contents Section 1 What Is Physics? Section 2 Measurements in Experiments Section 3 The Language of Physics

2. Chapter 1 Objectives Identify activities and fields that involve the major areas within physics. Describe the processes of the scientific method. Describe the role of models and diagrams in physics. Section 1 What Is Physics?

3. Chapter 1 The Branches of Physics Section 1 What Is Physics?

4. Chapter 1 Physics The goal of physics is to use a small number of basic concepts, equations, and assumptions to describe the physical world. These physics principles can then be used to make predictions about a broad range of phenomena. Physics discoveries often turn out to have unexpected practical applications, and advances in technology can in turn lead to new physics discoveries. Section 1 What Is Physics?

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

6. Chapter 1 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 the scientific method. Section 1 What Is Physics?

7. Chapter 1 Models Physics uses models that describe phenomena. A model is a pattern, plan, representation, or description designed to show the structure or workings of an object, system, or concept. A set of particles or interacting components considered to be a distinct physical entity for the purpose of study is called a system. Section 1 What Is Physics?

8. Chapter 1 Hypotheses Models help scientists develop hypotheses. A hypothesis is an explanation 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. Section 1 What Is Physics?

9. Chapter 1 Hypotheses, continued Galileo modeled the behavior of falling objects in order to develop a hypothesis about how objects fall. If heavier objects fell faster than slower ones,would two bricks of different masses tied together fall slower (b) or faster (c) than the heavy brick alone (a)? Because of this contradiction, Galileo hypothesized instead that all objects fall at the same rate, as in (d). Section 1 What Is Physics?

10. Chapter 1 Controlled Experiments A hypothesis must be tested in a controlled experiment. A controlled experiment tests only one factor at a time by using a comparison of a control group with an experimental group. Section 1 What Is Physics?

11. Section 2 Measurements in Experiments Chapter 1 Objectives List basic SI units and the quantities they describe. Convert measurements into scientific notation. Distinguish between accuracy and precision. Use significant figures in measurements and calculations.

12. Section 2 Measurements in Experiments Chapter 1 Numbers as Measurements In SI, the standard measurement system for science, there are seven base units. Each base unit describes a single dimension, such as length, mass, or time. The units of length, mass, and time are the meter (m), kilogram (kg), and second (s), respectively. Derived units are formed by combining the seven base units with multiplication or division. For example, speeds are typically expressed in units of meters per second (m/s).

13. Chapter 1 SI Standards Section 2 Measurements in Experiments

14. Section 2 Measurements in Experiments Chapter 1 SI Prefixes In SI, units are combined with prefixes that symbolize certain powers of 10. The most common prefixes and their symbols are shown in the table.

15. Section 2 Measurements in Experiments Chapter 1 Dimensions and Units Measurements of physical quantities must be expressed in units that match the dimensions of that quantity. In addition to having the correct dimension, measurements used in calculations should also have the same units. For example, when determining area by multiplying length and width, be sure the measurements are expressed in the same units.

16. Section 2 Measurements in Experiments Chapter 1 Sample Problem 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

17. 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.

18. 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.

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

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

21. Section 2 Measurements in Experiments Chapter 1 Significant Figures, continued Even though this ruler is marked in only centimeters and half-centimeters, if you estimate, you can use it to report measurements to a precision of a millimeter.

22. Chapter 1 Rules for Determining Significant Zeros Section 2 Measurements in Experiments

23. Chapter 1 Rules for Calculating with Significant Figures Section 2 Measurements in Experiments

24. Chapter 1 Rules for Rounding in Calculations Section 2 Measurements in Experiments

25. Section 3 The Language of Physics Chapter 1 Objectives Interpret data in tables and graphs, and recognize equations that summarize data. Distinguish between conventions for abbreviating units and quantities. Use dimensional analysis to check the validity of equations. Perform order-of-magnitude calculations.

26. Chapter 1 Mathematics and Physics Tables, graphs, and equations can make data easier to understand. For example, consider an experiment to test Galileo’s hypothesis that all objects fall at the same rate in the absence of air resistance. In this experiment, a table-tennis ball and a golf ball are dropped in a vacuum. The results are recorded as a set of numbers corresponding to the times of the fall and the distance each ball falls. A convenient way to organize the data is to form a table, as shown on the next slide. Section 3 The Language of Physics

27. Chapter 1 Data from Dropped-Ball Experiment Section 3 The Language of Physics A clear trend can be seen in the data. The more time that passes after each ball is dropped, the farther the ball falls.

28. Chapter 1 Graph from Dropped-Ball Experiment Section 3 The Language of Physics One method for analyzing the data is to construct a graph of the distance the balls have fallen versus the elapsed time since they were released. The shape of the graph provides information about the relationship between time and distance. Y= ax+b Y=ax^2+bx+c

29. Chapter 1 Physics Equations Physicists use equations to describe measured or predicted relationships between physical quantities. Variables and other specific quantities are abbreviated with letters that are boldfaced or italicized . Units are abbreviated with regular letters, sometimes called roman letters. Two tools for evaluating physics equations are dimensional analysis and order-of-magnitude estimates. Section 3 The Language of Physics

30. Chapter 1 Equation from Dropped-Ball Experiment We can use the following equation to describe the relationship between the variables in the dropped-ball experiment: (change in position in meters) = 4.9  (time in seconds) 2 With symbols, the word equation above can be written as follows : D y = 4.9( D t ) 2 The Greek letter D (delta) means “change in.” The abbreviation D y indicates the vertical change in a ball’s position from its starting point, and D t indicates the time elapsed. This equation allows you to reproduce the graph and make predictions about the change in position for any time. Section 3 The Language of Physics

31. Multiple Choice 1. What area of physics deals with the subjects of heat and temperature? A. mechanics B. thermodynamics C. electrodynamics D. quantum mechanics Standardized Test Prep Chapter 1

32. Multiple Choice 1. What area of physics deals with the subjects of heat and temperature? A. mechanics B. thermodynamics C. electrodynamics D. quantum mechanics Standardized Test Prep Chapter 1

33. Multiple Choice, continued 3. What term describes a set of particles or interacting components considered to be a distinct physical entity for the purpose of study? A. system B. model C. hypothesis D. controlled experiment Standardized Test Prep Chapter 1

34. Multiple Choice, continued 3. What term describes a set of particles or interacting components considered to be a distinct physical entity for the purpose of study? A. system B. model C. hypothesis D. controlled experiment Standardized Test Prep Chapter 1

35. Multiple Choice, continued 4. What is the SI base unit for length? F. inch G. foot H. meter J. kilometer Standardized Test Prep Chapter 1

36. Multiple Choice, continued 4. What is the SI base unit for length? F. inch G. foot H. meter J. kilometer Standardized Test Prep Chapter 1

37. Multiple Choice, continued Standardized Test Prep Chapter 1 5. A light-year (ly) is a unit of distance defined as the distance light travels in one year.Numerically, 1 ly = 9 500 000 000 000 km. How many meters are in a light-year? A. 9.5  10 10 m B. 9.5  10 12 m C. 9.5  10 15 m D. 9.5  10 18 m

38. Multiple Choice, continued 5. A light-year (ly) is a unit of distance defined as the distance light travels in one year.Numerically, 1 ly = 9 500 000 000 000 km. How many meters are in a light-year? A. 9.5  10 10 m B. 9.5  10 12 m C. 9.5  10 15 m D. 9.5  10 18 m Standardized Test Prep Chapter 1

39. Multiple Choice, continued 6. If you do not keep your line of sight directly over a length measurement, how will your measurement most likely be affected? F. Your measurement will be less precise. G. Your measurement will be less accurate. H. Your measurement will have fewer significant figures. J. Your measurement will suffer from instrument error. Standardized Test Prep Chapter 1

40. Multiple Choice, continued 6. If you do not keep your line of sight directly over a length measurement, how will your measurement most likely be affected? F. Your measurement will be less precise. G. Your measurement will be less accurate. H. Your measurement will have fewer significant figures. J. Your measurement will suffer from instrument error. Standardized Test Prep Chapter 1

41. Multiple Choice, continued 7. If you measured the length of a pencil by using the meterstick shown in the figure and you report your measurement in centimeters, how many significant figures should your reported measurement have? A. one B. two C. three D. four Standardized Test Prep Chapter 1

42. Multiple Choice, continued 7. If you measured the length of a pencil by using the meterstick shown in the figure and you report your measurement in centimeters, how many significant figures should your reported measurement have? A. one B. two C. three D. four Standardized Test Prep Chapter 1

43. Multiple Choice, continued 8. A room is measured to be 3.6 m by 5.8 m.What is the area of the room? (Keep significant figures in mind.) F. 20.88 m 2 G. 2  10 1 m 2 H. 2.0  10 1 m 2 J. 21 m 2 Standardized Test Prep Chapter 1

44. Multiple Choice, continued 8. A room is measured to be 3.6 m by 5.8 m.What is the area of the room? (Keep significant figures in mind.) F. 20.88 m 2 G. 2  10 1 m 2 H. 2.0  10 1 m 2 J. 21 m 2 Standardized Test Prep Chapter 1

45. Multiple Choice, continued 9. What technique can help you determine the power of 10 closest to the actual numerical value of a quantity? A. rounding B. order-of-magnitude estimation C. dimensional analysis D. graphical analysis Standardized Test Prep Chapter 1

46. Multiple Choice, continued 9. What technique can help you determine the power of 10 closest to the actual numerical value of a quantity? A. rounding B. order-of-magnitude estimation C. dimensional analysis D. graphical analysis Standardized Test Prep Chapter 1

47. Multiple Choice, continued 10. Which of the following statements is true of any valid physical equation? F. Both sides have the same dimensions. G. Both sides have the same variables. H. There are variables but no numbers. J. There are numbers but no variables. Standardized Test Prep Chapter 1

48. Multiple Choice, continued 10. Which of the following statements is true of any valid physical equation? F. Both sides have the same dimensions. G. Both sides have the same variables. H. There are variables but no numbers. J. There are numbers but no variables. Standardized Test Prep Chapter 1

49. Multiple Choice, continued The graph shows the relationship between time and distance for a ball dropped vertically from rest. Use the graph to answer questions 11–12. Standardized Test Prep Chapter 1 11. About how far has the ball fallen after 0.20 s? A. 5.00 cm B. 10.00 cm C. 20.00 cm D. 30.00 cm

50. Multiple Choice, continued The graph shows the relationship between time and distance for a ball dropped vertically from rest. Use the graph to answer questions 11–12. Standardized Test Prep Chapter 1 11. About how far has the ball fallen after 0.20 s? A. 5.00 cm B. 10.00 cm C. 20.00 cm D. 30.00 cm

51. Multiple Choice, continued Standardized Test Prep Chapter 1 12. Which statement best describes the relationship between the variables? F. For equal time intervals, the change in position is increasing. G. For equal time intervals, the change in position is decreasing. H. For equal time intervals, the change in position is constant. J. There is no clear relationship between time and change in position.

52. Multiple Choice, continued Standardized Test Prep Chapter 1 12. Which statement best describes the relationship between the variables? F. For equal time intervals, the change in position is increasing. G. For equal time intervals, the change in position is decreasing. H. For equal time intervals, the change in position is constant. J. There is no clear relationship between time and change in position.

53. Short Response Standardized Test Prep Chapter 1 13. Determine the number of significant figures in each of the following measurements. A. 0.0057 kg B. 5.70 g C. 6070 m D. 6.070  10 3 m

54. Short Response Standardized Test Prep Chapter 1 13. Determine the number of significant figures in each of the following measurements. A. 0.0057 kg B. 5.70 g C. 6070 m D. 6.070  10 3 m Answers: A. 2; B. 3; C. 3; D. 4

55. Short Response, continued Standardized Test Prep Chapter 1 14. Calculate the following sum, and express the answer in meters. Follow the rules for significant figures. (25.873 km) + (1024 m) + (3.0  10 2 cm)

56. Short Response, continued Standardized Test Prep Chapter 1 14. Calculate the following sum, and express the answer in meters. Follow the rules for significant figures. (25.873 km) + (1024 m) + (3.0  10 2 cm) Answer: 26 897 m

57. Short Response, continued Standardized Test Prep Chapter 1 15. Demonstrate how dimensional analysis can be used to find the dimensions that result from dividing distance by speed.

58. Short Response, continued Standardized Test Prep Chapter 1 15. Demonstrate how dimensional analysis can be used to find the dimensions that result from dividing distance by speed. Answer:

59. Extended Response Standardized Test Prep Chapter 1 16. You have decided to test the effects of four different garden fertilizers by applying them to four separate rows of vegetables. What factors should you control? How could you measure the results?

60. Extended Response Standardized Test Prep Chapter 1 16. You have decided to test the effects of four different garden fertilizers by applying them to four separate rows of vegetables. What factors should you control? How could you measure the results? Sample answer: Because the type of fertilizer is the variable being tested, all other factors should be controlled, including the type of vegetable, the amount of water, and the amount of sunshine. A fifth row with no fertilizer could be used as the control group. Results could be measured by size, quantity, appearance, and taste.

61. Extended Response, continued Standardized Test Prep Chapter 1 17. In a paragraph, describe how you could estimate the number of blades of grass on a football field.

62. Extended Response, continued Standardized Test Prep Chapter 1 17. In a paragraph, describe how you could estimate the number of blades of grass on a football field. Answer: Paragraphs should describe a process similar to the following: First, you could count the number of blades of grass in a small area, such as a 10 cm by 10 cm square. You would round this to the nearest order of magnitude, then multiply by the number of such squares along the length of the field, and then multiply again by the approximate number of such squares along the width of the field.