Chapter 1 INTRODUCTION The Science of Physics - PowerPoint Presentation

Slide1

Chapter

1

INTRODUCTION

The Science of PhysicsSlide2

Section 1

What is Physics

Chapter

1The Topics of Physics

Physics is simply the study of the physical world.Your goal in Physics is to use a small number of basic concepts, equations, and assumptions to describe the physical world.This will allow you to make predictions about a broad range of phenomena.Slide3

Section 1

What is Physics

Chapter

1The areas of Physics

1. Mechanics - The study of motion and its causes.Falling objects, friction, weight, spinning objects.2. Thermodynamics – The study of heat and temperature.Melting and Freezing processes, engines, refrigerators.3. Vibration and Wave Phenomena – The study of specific types of repetitive motion.Springs, pendulums, soundSlide4

Section 1

What is Physics

Chapter

1The areas of Physics (cont)

4. Optics – The study of light.Mirrors, lenses, color, astronomy5. Electromagnetism – The study of electricity, magnetism, and light.Electrical charge, circuitry, permanent magnets, electromagnets.6. Relativity – The study of particles moving at any speed, including very high speed.Particle collisions, particle accelerators, nuclear energy.Slide5

Section 1

What is Physics

Chapter

1The areas of Physics (cont.)

7. Quantum Mechanics – The study of submicroscopic particles.The atom and its partsSlide6

Types of observationsQualitative- descriptive, but not true measurements

HotLargeQuantitative- describe with numbers and units100C15 meters

Chapter

1Slide7

Section 1

What is Physics

Chapter

1The Scientific Method

The scientific method is a way to ask and answer scientific questions by making observations and doing experiments. Steps of the scientific : Observation (Ask a Question)Collect Data (Do Background Research)Construct a Hypothesis (Educated guess)Test Your Hypothesis by Doing Experiments Analyze Your Data and Draw a ConclusionThe conclusion is only valid if it can be verified by other people.Communicate Your ResultsSlide8

Chapter

1

The Scientific Method

Section 1

What is Physics?Slide9

Section 1

What is Physics

Chapter

1The Scientific Method (cont)

System – A set of items or interactions considered a distinct physical entity for the purpose of study.Decide what to study and eliminate everything else that has minimal or no effect on the problem.Draw a diagram of what remains (Model)Models – A replica or description designed to show the structure or workings of an object, system, or concept. Models help guide experimental designSlide10

Chapter

1

The System

Section 1

What is Physics?Slide11

Chapter

1

The Scientific Model

Section 1

What is Physics?Slide12

Section 1

What is Physics

Chapter

1The Scientific Method (cont)

Hypothesis – A reasonable explanation for observations, one that can be tested with additional experiments.The hypothesis must be tested in a controlled experiment.Controlled Experiment- Only one variable at a time is changed to determine what influences the phenomenon you are observing.Slide13

Section 2

Measurements in Experiments

Chapter

1Numbers As MeasurementsNumerical measurements in science contain the value (number) and Dimension. Dimension is the physical quantity being measured (length, mass, time, temperature, electric current)

Each dimension is measured using units and prefixes from the SI system.The dimension must match the unit. (ex. If you are measuring length, use the meter(m), not the kilogram(kg)Slide14

Section 2

Measurements in Experiments

Chapter

1SI is the standard measurement system for science.Used so that scientists can communicate with the same language.There are seven base units. They are:Meter(m) – lengthkilogram(kg) – MassSecond(s)

– TimeKelvin(K) – TemperatureAmpere(A) – currentMole(mol) – amount of substanceCandela(cd) – luminous intensitySlide15

How good are the measurements?

Scientists use two word to describe how good the measurements are:Accuracy- how close the measurement is to the actual value.Precision- how well can the measurement be repeated.Slide16

DifferencesAccuracy can be true of an individual measurement or the average of several.

Problems with accuracy are due to errorPrecision requires several measurements before anything can be said about it.Precision describes the limitation of the measuring instrument.Slide17

Percent Error

Percent error = (Experimental Value – Accepted value) x 100 Accepted ValuePercent error can be negative.Slide18

Percent Error

Absolute value of error

I know that I weigh 150 kg. If I weigh myself and the balance says 165 kg, what is the percent error?Slide19

Significant FiguresSlide20

Pacific

Atlantic

Present

Absent

If the decimal point is

absent

, start at the

A

tlantic (right), find the first non zero, and count all the rest of the digits

230000

1750Slide21

Pacific

Atlantic

Present

Absent

If the decimal point is

PRESENT

, start at the

P

acific (left), find the first non zero, and count all the rest of the digits

0.045

1.2300Slide22

Sig figs.How many sig figs in the following measurements?

458 g4085 g4850 g0.0485 g0.004085 g40.004085 g

405.0 g4050 g0.450 g

4050.05 g0.0500060 gSlide23

Rounding rules Look at the number behind the one you’re rounding.If it is 0 to 4 don’t change it.

If it is 5 to 9 make it one bigger.Round 45.462 to four sig figs=to three sig figs.to two sig figs.to one sig figs.

45.46

45.5

46.

50Slide24

Scientific notationAll non-zero digits in scientific notation are significant figures.Any ending zero will be after the decimal point to be significant1.20 x 10

3Sometimes you must write in scientific notation to use the correct sig figs.Slide25

Using your calculatorwith scientific notation

EE and EXP button stand for x 10 to the4.5 x 10-4 push 4.5push either EXP or EEpush 4 +/- or -4see what your display says.Slide26

Practice these problems

(4.8 x 10 5

) x (6.7 x 10-6)

(6.8 x 10 -6) (3.2 x 10 4)Remember when you multiply you add exponents106 x 10-4When you divide you subtract exponents.Slide27

Adding and SubtractingYou can’t add or subtract numbers until they are to the same power of ten.

Your calculator does this automatically.Remember- standard form starts with a number between 1 and 9 to start.Slide28

Adding and subtracting with sig figshave to round it to the least place of the measurement in the problem.Slide29

For example

27.93

6.4

+

First line up the decimal places

27.93

6.4

+

Then do the adding..

34.33

Find the estimated numbers in the problem.

27.9

3

6.

4

This answer must be rounded to the tenths place.Slide30

Practice4.8 + 6.8765520 + 94.980.0045 + 2.113500 -126

6.0 x 103 - 3.8 x 102 6.0 x 10-2 - 3.8 x 10-3 5.33 x 1022 - 3.8 x 1021Slide31

Multiplication and DivisionRule is simplerSame number of sig figs in the answer as the least in the question3.6 x 653

2350.83.6 has 2 s.f. 653 has 3 s.f.answer can only have 2 s.f.2400Slide32

Multiplication and DivisionSame rules for division.practice 4.5 / 6.245

4.5 x 6.2459.8764 x .0433.876 / 198016547 / 710Slide33

Fundamental Quantities and Their Dimension

Length [L]Mass [M]Time [T]other physical quantities can be constructed from these threeSlide34

Section 2

Measurements in Experiments

Chapter

1There are seven base units. They are:Meter(m) – lengthkilogram(kg) – MassSecond(s) – TimeKelvin(K)

– TemperatureAmpere(A) – currentMole(mol) – amount of substanceCandela(cd) – luminous intensitySlide35

Derived UnitsSlide36

Table 1.4, p.3

Metric PrefixesSlide37

Table 1.5, p.4Slide38

Volumecalculated by multiplying L x W x H

Liter the volume of a cube 1 dm (10 cm) on a side1L = 1 dm3so 1 L = 10 cm x 10 cm x 10 cm1 L = 1000 cm3 1/1000 L = 1 cm3 1 mL = 1 cm3 Slide39

Volume1 L about 1/4 of a gallon - a quart1 mL is about 20 drops of water or 1 sugar cubeSlide40

Mass1 gram is defined as the mass of 1 cm3 of water at 4 ºC.1000 g = 1000 cm

3 of water1 kg = 1 L of waterSlide41

Mass1 kg = 2.5 lbs1 g = 1 paper clip1 mg = 10 grains of saltSlide42

Converting

k

h

D

d

c

m

how far you have to move on this chart, tells you how far, and which direction to move the decimal place.

The box is the base unit, meters, Liters, grams, etc.Slide43

Conversion factors“A ratio of equivalent measurements.”Start with two things that are the same.

1 m = 100 cmCan divide by each side to come up with two ways of writing the number 1.Slide44

Conversion factors

100 cm

1 m

=

100 cm

100 cmSlide45

Conversion factors

1

1 m

=

100 cmSlide46

Conversion factors

1

1 m

=

100 cm

100 cm

=

1 m

1 m

1 mSlide47

Conversion factors

1

1 m

=

100 cm

100 cm

=

1 m

1Slide48

Conversion factorsA unique way of writing the number 1.In the same system they are defined quantities so they have unlimited significant figures.

Equivalence statements always have this relationship.big # small unit = small # big unit1000 mm = 1 m Slide49

Write the conversion factors for the followingkilograms to grams

feet to inches1.096 qt. = 1.00 LSlide50

What are they good for?

We can multiply by one creatively to change the units .

13 inches is how many yards?36 inches = 1 yard.

1 yard = 1 36 inches13 inches x 1 yard = 36 inchesSlide51

Conversion factorsCalled conversion factors because they allow us to convert units.Really just multiplying by one, in a creative way.Choose the conversion factor that gets rid of the unit you don’t want.Slide52

Dimensional AnalysisDimension = unitAnalyze = solveUsing the units to solve the problems.

If the units of your answer are right, chances are you did the math right.Slide53

Dimensional AnalysisUsing with metric unitsNeed to know equivalence statements

If it has a prefix, get rid of it with one conversion factorTo add a prefix use a conversion factorSlide54

Practice25 mL is how many L?

5.8 x 10-6 mm is how many nm?Slide55

Dimensional AnalysisIn the same system, unlimited sig figsFrom one system to another. The conversion factor has as many the most sig figs in the measurements.

1 inch is 2.54 cm 3 sf

1 inch

2.54 cmSlide56

Dimensional AnalysisA race is 10.0 km long. How far is this in miles? 1 mile = 1760 yds

1 meter = 1.094 ydsSlide57

Dimensional AnalysisPikes peak is 14,110 ft above sea level. What is this in meters? 1 mile = 1760 yds

1 meter = 1.094 ydsSlide58

Dimensional AnalysisAnother measuring system has different units of measure. 6 ft = 1 fathom 100 fathoms = 1 cable length 10 cable lengths = 1 nautical mile 3 nautical miles = 1 leagueJules Verne wrote a book 20,000 leagues under the sea. How far is this in feet?Slide59

Multiple unitsThe speed limit is 65 mi/hr. What is this in m/s?

1 mile = 1760 yds 1 meter = 1.094 yds

65 mi

hr

1760 yd

1 mi

1.094 yd

1 m

1

hr

60

min

1

min

60

sSlide60

Multiple unitsLead has a density of 11.4 g/mL. What is this in pounds per quart?454 g = 1 lb1 L = 1.06 qtSlide61

Units to a PowerHow many m3 is 1500 cm3

?1500 cm3

1 m

100 cm

1 m

100 cm

1 m

100 cm

1500 cm

3

1 m

100 cm

3Slide62

Units to a PowerHow many cm2 is 15 m2?

36 cm3 is how many mm3?Slide63

A European cheese making recipe calls for 2.50 kg of whole milk. An American wishes to make the recipe has only measuring cups, which are marked in cups. If the density of milk is 1.03 g/cm3 how many cups of milk does he need?

1 qt = 2 pints

1 yd = 3 ft.

1 mile = 1.61 km1 m = 1.094 yds1 L = 1000 cm3

1 gal = 4 qt1 L = 1.06 qt1 lb = 454 g1 mi =1760 yds

1 pint = 2 cupsSlide64

A barrel of petroleum holds 42.0 gal. Empty it weighs 75 lbs. When it is filled with ethanol it weighs 373 lbs. What is the density of ethanol in g/cm3?

1 qt = 2 pints

1 yd = 3 ft.

1 mile = 1.61 km1 m = 1.094 yds1 L = 1000 cm3

1 gal = 4 qt1 L = 1.06 qt1 lb = 454 g1 mi =1760 yds1 pint = 2 cups