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 We can’t control Earth’s motion, but we have learned the rules by which it moves. The study of nature’s rules is what this course is about. Understanding.

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Presentation on theme: " We can’t control Earth’s motion, but we have learned the rules by which it moves. The study of nature’s rules is what this course is about. Understanding."— Presentation transcript:

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2  We can’t control Earth’s motion, but we have learned the rules by which it moves. The study of nature’s rules is what this course is about. Understanding these rules adds richness to the way we see our world.  Physics is about the nature of basic things, motion, forces, energy, matter, heat, sound, light and the composition of atoms.

3 -Physics can be used to explain anything in the physical world, it is the study of the physical world -We are surrounded by the principles of physics every day -You probably know more about physics than you realize. - When you buy ice cream, you immediately put it in the freezer immediately because you instinctively know enough about the laws of physics to understand that if you leave it out, it will melt

4  You can understand other sciences much better if you first understand physics. Physics is the most basic of all the sciences. Chemistry is about how matter is put together. Biology is still more complex and involves matter that is alive.

5 Chapter 1 Section 1 What Is Physics? Which branch of physics does Ice cream melting belong in?

6  When scientific findings in nature are expressed mathematically, they are easier to verify or to disprove by experiment.  When the ideas of science are expressed in mathematical terms, they are unambiguous.  The equations of science provide compact expressions of relationships between concepts.

7 Chapter 1  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?

8 Chapter 1 Section 1 What Is Physics?

9 Chapter 1  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.  Why do we use the scientific method?  Sometimes our senses deceive us. Section 1 What Is Physics?

10 Copyright © Houghton Mifflin Company. All rights reserved. 1| 10 Lines “a” and “b” are equal in length! Section 1.3

11 Copyright © Houghton Mifflin Company. All rights reserved. 1| 11 The lines are all horizontal! Section 1.3

12 Copyright © Houghton Mifflin Company. All rights reserved. 1| 12 Section 1.3

13 Copyright © Houghton Mifflin Company. All rights reserved. 1| 13 Section 1.3

14  Who can tell me the steps of the scientific method? Scientific methods generally include some, if not all, of the following: 1. Recognize a problem. 2. Make an educated guess—a hypothesis—about the answer. 3. Predict the consequences of the hypothesis. 4. Perform experiments to test predictions. 5. Formulate the simplest general rule that organizes the main ingredients: hypothesis, prediction, and experimental outcome.

15  If a scientist finds evidence that contradicts a hypothesis, law, or principle, then the hypothesis, law, or principle must be changed or abandoned.  In science, a fact is a close agreement by competent observers who make a series of observations of the same phenomenon.  A scientific hypothesis is an educated guess that is not fully accepted until demonstrated by experiment.

16  When hypotheses about the relationship among natural quantities are tested over and over again and not contradicted, they may become laws or principles  Scientists must accept their findings even when they would like them to be different.  They must distinguish between what they see and what theywish to see.  In other words be objective!

17  A scientific theory is a synthesis of a large body of information that encompasses well- tested and verified hypotheses about certain aspects of the natural world.  The theories of science evolve as they go through stages of redefinition and refinement.  Better hypotheses are made by those who are honest in the face of experimental evidence.

18 Chapter 1  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?

19 Chapter 1  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?

20  A scientific hypothesis must be testable. It is more important that there be a way of proving it wrong than that there be a way of proving it correct. (support/reject) If there is no test for its possible wrongness, then it is not scientific.  Here is a hypothesis that is scientific: › “No material object can travel faster than light.”  Even if it were supported by a thousand other experiments, this hypothesis could be proven wrong by a single experiment. (So far, we find it to be true.)

21  Here are hypotheses that are not scientific: The hypothesis: “The alignment of planets in the sky determines the best time for making decisions” cannot be proven wrong, nor can it be proven right. It is speculation. The hypothesis: “Intelligent life exists on other planets somewhere in the universe” can be proven correct, but there is no way to prove it wrong if no life is ever found. The hypothesis: “Most people stop for red lights” doesn’t link up to our general understanding of nature, so it doesn’t fit into the structure of science.

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23 think! Which of these is a scientific hypothesis? a. Atoms are the smallest particles of matter. b. The universe is surrounded by a second universe, the existence of which cannot be detected by scientists. c. Albert Einstein was the greatest physicist of the 1900s. Answer: (a) is scientific, because there is a test for its wrongness. (b) has no test for possible wrongness and is therefore unscientific. (c) is an assertion that has no test for possible wrongness.

24 Chapter 1  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?

25 Section 2 Measurements in Experiments Chapter 1  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.

26 Section 2 Measurements in Experiments Chapter 1  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).

27 Section 2 Measurements in Experiments Chapter 1 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.

28 Section 2 Measurements in Experiments Chapter 1  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.

29 Section 2 Measurements in Experiments Chapter 1 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

30 Section 2 Measurements in Experiments Chapter 1 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.

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

32 Section 2 Measurements in Experiments Chapter 1  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.

33  A—Good precision and accuracy  B—Some accuracy and poor precision  C—Good precision and poor accuracy  D—Poor precision and accuracy ABCD

34  When shooting free throws, is it better to be precise or accurate?

35  It’s better to be accurate.

36 Section 2 Measurements in Experiments Chapter 1  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.

37 Chapter 1 Section 2 Measurements in Experiments

38 Chapter 1 Section 2 Measurements in Experiments

39 Chapter 1 Section 2 Measurements in Experiments


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