Chapter 1 introduction of physic for student

Physic

1. Physics for Scientists and Physics for Scientists and
EngineersEngineers
Introduction Introduction
andand
Chapter 1Chapter 1

2. PhysicsPhysics

Fundamental ScienceFundamental Science

concerned with the basic principles of the Universeconcerned with the basic principles of the Universe

foundation of other physical sciencesfoundation of other physical sciences

Divided into major areas asDivided into major areas as

Classical MechanicsClassical Mechanics

RelativityRelativity

ThermodynamicsThermodynamics

ElectromagnetismElectromagnetism

OpticsOptics

Quantum MechanicsQuantum Mechanics

3. Classical PhysicsClassical Physics

Mechanics and electromagnetism are basic Mechanics and electromagnetism are basic
to all other branches of classical physicsto all other branches of classical physics

Classical physics developed before 1900Classical physics developed before 1900

Our study will start with Classical Our study will start with Classical
MechanicsMechanics

Also called Newtonian MechanicsAlso called Newtonian Mechanics

4. Classical PhysicsClassical Physics

Includes MechanicsIncludes Mechanics

Major developments by Newton, and continuing Major developments by Newton, and continuing
through the latter part of the 19through the latter part of the 19
thth
century century

ThermodynamicsThermodynamics

OpticsOptics

ElectromagnetismElectromagnetism

All of these were not developed until the latter part All of these were not developed until the latter part
of the 19of the 19
thth
century century

5. Modern PhysicsModern Physics

Began near the end of the 19Began near the end of the 19
thth
century century

Phenomena that could not be explained by Phenomena that could not be explained by
classical physicsclassical physics

Includes theories of relativity and quantum Includes theories of relativity and quantum
mechanicsmechanics

6. Classical Mechanics TodayClassical Mechanics Today

Still important in many disciplinesStill important in many disciplines

Wide range of phenomena that can be Wide range of phenomena that can be
explained with classical mechanicsexplained with classical mechanics

Many basic principles carry over into other Many basic principles carry over into other
phenomenaphenomena

Conservation Laws also apply directly to Conservation Laws also apply directly to
other areasother areas

7. Objective of PhysicsObjective of Physics

To find the limited number of fundamental To find the limited number of fundamental
laws that govern natural phenomenalaws that govern natural phenomena

To use these laws to develop theories that To use these laws to develop theories that
can predict the results of future can predict the results of future
experimentsexperiments

Express the laws in the language of Express the laws in the language of
mathematicsmathematics

8. Theory and ExperimentsTheory and Experiments

Should complement each otherShould complement each other

When a discrepancy occurs, theory may be When a discrepancy occurs, theory may be
modifiedmodified

Theory may apply to limited conditionsTheory may apply to limited conditions

Example: Newtonian Mechanics is confined to objects Example: Newtonian Mechanics is confined to objects
traveling slowing with respect to the speed of lighttraveling slowing with respect to the speed of light

Try to develop a more general theTry to develop a more general theoryory

9. Quantities UsedQuantities Used

In mechanics, three In mechanics, three basic quantitiesbasic quantities are used are used

LengthLength

MassMass

TimeTime

Will also use Will also use derived quantitiesderived quantities

These are other quantities can be expressed in These are other quantities can be expressed in
terms of theseterms of these

10. Standards of QuantitiesStandards of Quantities

Standardized systemsStandardized systems

agreed upon by some authority, usually a agreed upon by some authority, usually a
governmental bodygovernmental body

SI – Systéme InternationalSI – Systéme International

agreed to in 1960 by an international agreed to in 1960 by an international
committeecommittee

main system used in this textmain system used in this text

11. LengthLength

UnitsUnits

SI – meter, mSI – meter, m

Defined in terms of a meter – the Defined in terms of a meter – the
distance traveled by light in a vacuum distance traveled by light in a vacuum
during a given timeduring a given time

12. Table 1.1, p. 5

13. MassMass

UnitsUnits

SI – kilogram, kgSI – kilogram, kg

Defined in terms of a kilogram, based Defined in terms of a kilogram, based
on a specific cylinder kept at the on a specific cylinder kept at the
International Bureau of StandardsInternational Bureau of Standards

14. Table 1.2, p. 5

15. Standard KilogramStandard Kilogram
The National Standard Kilogram The National Standard Kilogram
No. 20, an accurate copy of the No. 20, an accurate copy of the
International Standard Kilogram International Standard Kilogram
kept at Sèvres, France, is housed kept at Sèvres, France, is housed
under a double bell jar in a vault under a double bell jar in a vault
at the National Institute of at the National Institute of
Standards and Technology. Standards and Technology.

16. TimeTime

UnitsUnits

seconds, sseconds, s

Defined in terms of the oscillation of Defined in terms of the oscillation of
radiation from a cesium atomradiation from a cesium atom

17. Table 1.3, p. 6

18. Number NotationNumber Notation

When writing out numbers with many When writing out numbers with many
digits, spacing in groups of three will digits, spacing in groups of three will
be usedbe used

No commasNo commas

Examples:Examples:

25 100 25 100

5.123 456 789 125.123 456 789 12

19. Reasonableness of ResultsReasonableness of Results

When solving a problem, you need to When solving a problem, you need to
check your answer to see if it seems check your answer to see if it seems
reasonablereasonable

Reviewing the tables of approximate Reviewing the tables of approximate
values for length, mass, and time will values for length, mass, and time will
help you test for reasonablenesshelp you test for reasonableness

20. Systems of MeasurementsSystems of Measurements

US CustomaryUS Customary

everyday unitseveryday units

Length is measured in feetLength is measured in feet

Time is measured in secondsTime is measured in seconds

Mass is measured in slugsMass is measured in slugs

often uses weight, in pounds, instead of mass often uses weight, in pounds, instead of mass
as a fundamental quantityas a fundamental quantity

21. PrefixesPrefixes

Prefixes correspond to powers of 10Prefixes correspond to powers of 10

Each prefix has a specific nameEach prefix has a specific name

Each prefix has a specific abbreviationEach prefix has a specific abbreviation

22. PrefixesPrefixes

The prefixes can The prefixes can
be used with any be used with any
base unitsbase units

They are They are
multipliers of the multipliers of the
base unitbase unit

Examples:Examples:

1 mm = 101 mm = 10
-3-3
m m

1 mg = 101 mg = 10
-3-3
g g

23. Model BuildingModel Building

A A modelmodel is a system of physical is a system of physical
componentscomponents

Identify the componentsIdentify the components

Make predictions about the behavior of the Make predictions about the behavior of the
systemsystem

The predictions will be based on interactions The predictions will be based on interactions
among the components and/oramong the components and/or

Based on the interactions between the Based on the interactions between the
components and the environmentcomponents and the environment

24. Models of MatterModels of Matter

Some Greeks Some Greeks
thought matter is thought matter is
made of atomsmade of atoms

JJ Thomson (1897) JJ Thomson (1897)
found electrons and found electrons and
showed atoms had showed atoms had
structurestructure

Rutherford (1911) Rutherford (1911)
central nucleus central nucleus
surrounded by surrounded by
electronselectrons

25. Models of MatterModels of Matter

Nucleus has structure, containing Nucleus has structure, containing
protons and neutronsprotons and neutrons

Number of protons gives atomic numberNumber of protons gives atomic number

Number of protons and neutrons gives Number of protons and neutrons gives
mass numbermass number

Protons and neutrons are made up of Protons and neutrons are made up of
quarksquarks

26. Modeling TechniqueModeling Technique

Important technique is to build a Important technique is to build a
model for a problemmodel for a problem

Identify a system of physical Identify a system of physical
components for the problemcomponents for the problem

Make predictions of the behavior of the Make predictions of the behavior of the
system based on the interactions among system based on the interactions among
the components and/or the components the components and/or the components
and the environmentand the environment

27. DensityDensity

Density is an example of a Density is an example of a derivedderived
quantityquantity

It is defined as mass per unit volumeIt is defined as mass per unit volume

Units are kg/mUnits are kg/m
33
m
V


28. Table 1.5, p.9

29. Atomic MassAtomic Mass

The atomic mass is the total number The atomic mass is the total number
of protons and neutrons in the of protons and neutrons in the
elementelement

Can be measured in Can be measured in atomic mass atomic mass
unitsunits, u, u

1 u = 1.6605387 x 101 u = 1.6605387 x 10
-27-27
kg kg

30. Basic Quantities and Their Basic Quantities and Their
DimensionDimension
Dimension has a specific meaning – it Dimension has a specific meaning – it
denotes the physical nature of a denotes the physical nature of a
quantityquantity
Dimensions are denoted with square Dimensions are denoted with square
bracketsbrackets
Length [L]Length [L]
Mass [M]Mass [M]
Time [T]Time [T]

31. Dimensional AnalysisDimensional Analysis
Dimensional Analysis is a technique to check Dimensional Analysis is a technique to check
the correctness of an equation or to assist in the correctness of an equation or to assist in
deriving an equationderiving an equation
Dimensions (Dimensions (length, mass, time, length, mass, time,
combinationscombinations) can be treated as algebraic ) can be treated as algebraic
quantities quantities
add, subtract, multiply, divideadd, subtract, multiply, divide
Both sides of equation must have the same Both sides of equation must have the same
dimensionsdimensions

32. SymbolsSymbols
The symbol used in an equation is not The symbol used in an equation is not
necessarily the symbol used for its dimensionnecessarily the symbol used for its dimension
Some quantities have one symbol used Some quantities have one symbol used
consistentlyconsistently
For example, time is For example, time is tt virtually all the time virtually all the time
Some quantities have many symbols used, Some quantities have many symbols used,
depending upon the specific situationdepending upon the specific situation
For example, lengths may be For example, lengths may be xx,, yy,, zz,, rr,, dd,, hh, etc., etc.

33. Dimensional AnalysisDimensional Analysis
Given the equation: Given the equation: x = ½ at x = ½ at
22
Check dimensions on each side:Check dimensions on each side:
TheThe T
2
’s cancel, leaving cancel, leaving L for the for the
dimensions of each sidedimensions of each side
The equation is dimensionally correctThe equation is dimensionally correct
LT
T
L
L
2
2


34. Conversion of UnitsConversion of Units

When units are not consistent, you may When units are not consistent, you may
need to convert to appropriate onesneed to convert to appropriate ones

Units can be treated like algebraic Units can be treated like algebraic
quantities that can cancel each other outquantities that can cancel each other out

See the inside of the front cover of your See the inside of the front cover of your
textbook for an extensive list of conversion textbook for an extensive list of conversion
factorsfactors

35. ConversionConversion
Always include units for every quantity, you Always include units for every quantity, you
can carry the units through the entire can carry the units through the entire
calculationcalculation
Multiply original value by a ratio equal to Multiply original value by a ratio equal to
oneone
ExampleExample
cm1.38
in1
cm54.2
in0.15
cm?in0.15








36. Significant FiguresSignificant Figures
A significant figure is one that is reliably A significant figure is one that is reliably
knownknown
Zeros may or may not be significantZeros may or may not be significant
Those used to position the decimal point are Those used to position the decimal point are
not significantnot significant
To remove ambiguity, use scientific notationTo remove ambiguity, use scientific notation
In a measurement, the significant figures In a measurement, the significant figures
include the first estimated digitinclude the first estimated digit

37. Significant FiguresSignificant Figures
0.0075 m 0.0075 m has 2 significant figureshas 2 significant figures
The leading zeros are placeholders onlyThe leading zeros are placeholders only
Can write in scientific notation to show more clearly: Can write in scientific notation to show more clearly:
7.5 x 10-7.5 x 10-
33
m m for 2 significant figuresfor 2 significant figures
10.0 m 10.0 m has 3 significant figureshas 3 significant figures
The decimal point gives information about the The decimal point gives information about the
reliability of the measurementreliability of the measurement
1500 m1500 m is ambiguous is ambiguous
Use Use 1.5 x 101.5 x 10
33
m m for 2 significant figuresfor 2 significant figures
Use Use 1.50 x 101.50 x 10
33
m m for 3 significant figuresfor 3 significant figures
Use Use 1.500 x 101.500 x 10
33
m m for 4 significant figuresfor 4 significant figures

38. Operations with Significant Figures – Operations with Significant Figures –
Multiplying or DividingMultiplying or Dividing
When multiplying or dividing, the number of When multiplying or dividing, the number of
significant figures in the final answer is the significant figures in the final answer is the
same as the number of significant figures in the same as the number of significant figures in the
quantity having the lowest number of significant quantity having the lowest number of significant
figures.figures.
Example: Example: 25.57 m x 2.45 m = 62.6 m25.57 m x 2.45 m = 62.6 m
22
The The 2.45 m2.45 m limits your result to 3 significant limits your result to 3 significant
figuresfigures

39. Operations with Significant Figures – Operations with Significant Figures –
Adding or SubtractingAdding or Subtracting

When adding or subtracting, the number of When adding or subtracting, the number of
decimal places in the result should equal the decimal places in the result should equal the
smallest number of decimal places in any smallest number of decimal places in any
term in the sum.term in the sum.

Example: Example: 135 cm + 3.25 cm = 138 cm135 cm + 3.25 cm = 138 cm

The The 135 cm 135 cm limits your answer to the units limits your answer to the units
decimal valuedecimal value

40. Operations With Significant Figures – Operations With Significant Figures –
Summary Summary

The rule for addition and subtraction are The rule for addition and subtraction are
different than the rule for multiplication and different than the rule for multiplication and
divisiondivision

For adding and subtracting, the For adding and subtracting, the number of number of
decimal placesdecimal places is the important is the important
considerationconsideration

For multiplying and dividing, the For multiplying and dividing, the number of number of
significant figuressignificant figures is the important is the important
considerationconsideration

41. RoundingRounding

Last retained digit is increased by 1 if the Last retained digit is increased by 1 if the
last digit dropped is 5 or abovelast digit dropped is 5 or above

Last retained digit remains as it is if the last Last retained digit remains as it is if the last
digit dropped is less than 5 digit dropped is less than 5

If the last digit dropped is equal to 5, the If the last digit dropped is equal to 5, the
retained digit should be rounded to the retained digit should be rounded to the
nearest even numbernearest even number

Saving rounding until the final result will Saving rounding until the final result will
help eliminate accumulation of errorshelp eliminate accumulation of errors

42. 
Explain the problem with your own words.Explain the problem with your own words.

Make a good picture describing the problemMake a good picture describing the problem

Write down the given data with their units. Convert all Write down the given data with their units. Convert all
data into S.I. system.data into S.I. system.

Identify the unknowns.Identify the unknowns.

Find the connections between the unknowns and the data.Find the connections between the unknowns and the data.

Write the physical equations that can be applied to the Write the physical equations that can be applied to the
problem.problem.

Solve those equations. Solve those equations.

Check if the values obtained are reasonable Check if the values obtained are reasonable  order of order of
magnitude and units.magnitude and units.
Problem solving tacticsProblem solving tactics

43. Reasonableness of ResultsReasonableness of Results

When solving a problem, you need to When solving a problem, you need to
check your answer to see if it seems check your answer to see if it seems
reasonablereasonable

Reviewing the tables of approximate Reviewing the tables of approximate
values for length, mass, and time will help values for length, mass, and time will help
you test for reasonablenessyou test for reasonableness