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Chapter 1. Section 1 What Is Physics?. Objectives. Identify Physics and describe the activities and fields that involve the major areas within physics. Describe the processes of the scientific method. Describe how a controlled experiment can be used to test a hypothesis. Chapter 1.

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objectives

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.
slide2

Chapter 1

Section 1 What Is Physics?

physics

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.
the 7 branches of physics

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

slide5

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

slide6

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

physics and technology

Chapter 1

Section 1 What Is Physics?

Physics and Technology
the scientific method

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.
steps of the scientific method

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.

hypotheses

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.
galileo s hypotheses

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?
galileo s hypothesis

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.
controlled experiments

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.

objectives1

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.
slide15

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

si prefixes

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.

si unit conversion

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

sample problem continued

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.

sample problem continued1

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.

unit conversions

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

accuracy and precision

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.
significant figures

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.
always significant

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

never significant

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

slide26

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

slide27

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

objectives2

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.
slide29

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.

graphs

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.

equations

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
manipulating equations

Section 3 The Language of Physics

Chapter 1

Manipulating Equations

Speed

s = d

t

Force

F = m x a

equation from dropped ball experiment

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.