we can’t control earth’s motion, but we have learned the rules by which it moves. the study of...

PHYSICS!!Science is the study of nature’s rules.

Science is the study of nature’s

rules.

What is Physics About?

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.

What is Physics

-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. http://www.teachertube.com/viewVideo.php?video_id=190086

http://www.teachertube.com/viewVideo.php?video_id=190086

http://www.teachertube.com/viewVideo.php?video_id=190086

The Basis of Science

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.

Chapter 1

The Branches of Physics

Section 1 What Is Physics?

Which branch of

physics does Ice

cream meltin

g

belong in?

Why so much MATH???

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.

Chapter 1Physics

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.


http://www.imdb.com/title/tt1386703/

Chapter 1Physics and Technology


Chapter 1The 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.

Why do we use the scientific method?

Sometimes our senses deceive us.


Some Optical Illusions

Copyright © Houghton Mifflin Company. All rights reserved. 1| 10

Lines “a” and “b” are equal in length!

Section 1.3

Optical Illusions

Copyright © Houghton Mifflin Company. All rights reserved. 1| 11

The lines are all horizontal!

Section 1.3

The Scientific Method 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.

A Scientific Attitude 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.

A Scientific Attitude

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 findingseven 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!

Scientific Theories

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.

Chapter 1Models

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.


Chapter 1Hypotheses

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.


Scientific Hypothesis

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.)

Hypotheses that are NOT scientific

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.

Experiments are conducted to test scientific hypotheses.

Scientific Hypothesis

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.

Chapter 1Controlled 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 2 Measurements in ExperimentsChapter 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.


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).


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.


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.


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


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.

–15

–15

1 10 g 1 fg and

1 fg 1 10 g

–15–151 10 g

(2.0 fg) = 2.0 10 g1 fg


Sample Problem, continued

Take the previous answer, and use a similar process to

cancel the units of grams to give units of kilograms. –15 –18

3

1 kg(2.0 10 g) = 2.0 10 kg

1 10 g


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.

PRECISION VS. ACCURACY

A—Good precision and accuracy

B—Some accuracy and poor precision

C—Good precision and poor accuracy

D—Poor precision and accuracy

A B C D

Discussion Question

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

It’s better to be accurate.


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.

Chapter 1Rules for Determining Significant Zeros

Section 2 Measurements in Experiments

Chapter 1

Rules for Calculating with Significant Figures


Chapter 1Rules for Rounding in Calculations


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