Chapter 1 introduction of physic for student

Physics for Scientists and
Physics for Scientists and
Engineers
Engineers
Introduction
Introduction
and
and
Chapter 1
Chapter 1

Physics
Physics
 Fundamental Science
Fundamental Science

concerned with the basic principles of the Universe
concerned with the basic principles of the Universe

foundation of other physical sciences
foundation of other physical sciences
 Divided into major areas as
Divided into major areas as

Classical Mechanics
Classical Mechanics

Relativity
Relativity

Thermodynamics
Thermodynamics

Electromagnetism
Electromagnetism

Optics
Optics

Quantum Mechanics
Quantum Mechanics

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

Classical Physics
Classical Physics

Includes Mechanics
Includes Mechanics

Major developments by Newton, and continuing
Major developments by Newton, and continuing
through the latter part of the 19
through the latter part of the 19th
th
century
century

Thermodynamics
Thermodynamics

Optics
Optics

Electromagnetism
Electromagnetism

All of these were not developed until the latter part
All of these were not developed until the latter part
of the 19
of the 19th
th
century
century

Modern Physics
Modern Physics

Began near the end of the 19
Began near the end of the 19th
th
century
century

Phenomena that could not be explained by
Phenomena that could not be explained by
classical physics
classical physics

Includes theories of relativity and quantum
Includes theories of relativity and quantum
mechanics
mechanics

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

Objective of Physics
Objective of Physics
 To find the limited number of fundamental
To find the limited number of fundamental
laws that govern natural phenomena
laws 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
experiments
experiments
 Express the laws in the language of
Express the laws in the language of
mathematics
mathematics

Theory and Experiments
Theory and Experiments

Should complement each other
Should complement each other

When a discrepancy occurs, theory may be
When a discrepancy occurs, theory may be
modified
modified

Theory may apply to limited conditions
Theory 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 light
traveling slowing with respect to the speed of light

Try to develop a more general the
Try to develop a more general theory
ory

Quantities Used
Quantities Used
 In mechanics, three
In mechanics, three basic quantities
basic quantities are used
are used

Length
Length

Mass
Mass

Time
Time
 Will also use
Will also use derived quantities
derived quantities

These are other quantities can be expressed in
These are other quantities can be expressed in
terms of these
terms of these

Standards of Quantities
Standards of Quantities

Standardized systems
Standardized systems

agreed upon by some authority, usually a
agreed upon by some authority, usually a
governmental body
governmental body

SI – Systéme International
SI – Systéme International

agreed to in 1960 by an international
agreed to in 1960 by an international
committee
committee

main system used in this text
main system used in this text

Length
Length

Units
Units

SI – meter, m
SI – 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 time
during a given time

Mass
Mass

Units
Units

SI – kilogram, kg
SI – 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 Standards
International Bureau of Standards

Standard Kilogram
Standard 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.

Time
Time

Units
Units

seconds, s
seconds, s

Defined in terms of the oscillation of
Defined in terms of the oscillation of
radiation from a cesium atom
radiation from a cesium atom

Number Notation
Number 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 used
be used

No commas
No commas

Examples:
Examples:

25 100
25 100

5.123 456 789 12
5.123 456 789 12

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

Systems of Measurements
Systems of Measurements

US Customary
US Customary

everyday units
everyday units

Length is measured in feet
Length is measured in feet

Time is measured in seconds
Time is measured in seconds

Mass is measured in slugs
Mass is measured in slugs

often uses weight, in pounds, instead of mass
often uses weight, in pounds, instead of mass
as a fundamental quantity
as a fundamental quantity

Prefixes
Prefixes

Prefixes correspond to powers of 10
Prefixes correspond to powers of 10

Each prefix has a specific name
Each prefix has a specific name
 Each prefix has a specific abbreviation
Each prefix has a specific abbreviation

Prefixes
Prefixes
 The prefixes can
The prefixes can
be used with any
be used with any
base units
base units
 They are
They are
multipliers of the
multipliers of the
base unit
base unit
 Examples:
Examples:

1 mm = 10
1 mm = 10-3
-3
m
m

1 mg = 10
1 mg = 10-3
-3
g
g

Model Building
Model Building
 A
A model
model is a system of physical
is a system of physical
components
components

Identify the components
Identify the components

Make predictions about the behavior of the
Make predictions about the behavior of the
system
system

The predictions will be based on interactions
The predictions will be based on interactions
among the components and/or
among the components and/or

Based on the interactions between the
Based on the interactions between the
components and the environment
components and the environment

Models of Matter
Models of Matter
 Some Greeks
Some Greeks
thought matter is
thought matter is
made of atoms
made of atoms
 JJ Thomson (1897)
JJ Thomson (1897)
found electrons and
found electrons and
showed atoms had
showed atoms had
structure
structure
 Rutherford (1911)
Rutherford (1911)
central nucleus
central nucleus
surrounded by
surrounded by
electrons
electrons

Models of Matter
Models of Matter

Nucleus has structure, containing
Nucleus has structure, containing
protons and neutrons
protons and neutrons

Number of protons gives atomic number
Number of protons gives atomic number

Number of protons and neutrons gives
Number of protons and neutrons gives
mass number
mass number

Protons and neutrons are made up of
Protons and neutrons are made up of
quarks
quarks

Modeling Technique
Modeling Technique

Important technique is to build a
Important technique is to build a
model for a problem
model for a problem

Identify a system of physical
Identify a system of physical
components for the problem
components 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 environment
and the environment

Density
Density

Density is an example of a
Density is an example of a derived
derived
quantity
quantity

It is defined as mass per unit volume
It is defined as mass per unit volume

Units are kg/m
Units are kg/m3
3
m
V
 

Atomic Mass
Atomic 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
element
element

Can be measured in
Can be measured in atomic mass
atomic mass
units
units, u
, u

1 u = 1.6605387 x 10
1 u = 1.6605387 x 10-27
-27
kg
kg

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

Dimensional 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 equation
deriving an equation
 Dimensions (
Dimensions (length, mass, time,
length, mass, time,
combinations
combinations) can be treated as algebraic
) can be treated as algebraic
quantities
quantities
 add, subtract, multiply, divide
add, subtract, multiply, divide
 Both sides of equation must have the same
Both sides of equation must have the same
dimensions
dimensions

Symbols
Symbols
 The symbol used in an equation is not
The symbol used in an equation is not
necessarily the symbol used for its dimension
necessarily the symbol used for its dimension
 Some quantities have one symbol used
Some quantities have one symbol used
consistently
consistently
 For example, time is
For example, time is t
t virtually all the time
virtually all the time
 Some quantities have many symbols used,
Some quantities have many symbols used,
depending upon the specific situation
depending upon the specific situation
 For example, lengths may be
For example, lengths may be x
x,
, y
y,
, z
z,
, r
r,
, d
d,
, h
h, etc.
, etc.

 Given the equation:
Given the equation: x = ½ at
x = ½ at 2
2
 Check dimensions on each side:
Check dimensions on each side:
 The
The T2
’s cancel, leaving
cancel, leaving L for the
for the
dimensions of each side
dimensions of each side
 The equation is dimensionally correct
The equation is dimensionally correct
L
T
T
L
L 2
2




Conversion of Units
Conversion of Units
 When units are not consistent, you may
When units are not consistent, you may
need to convert to appropriate ones
need to convert to appropriate ones
 Units can be treated like algebraic
Units can be treated like algebraic
quantities that can cancel each other out
quantities 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
factors
factors

Conversion
Conversion
 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
calculation
calculation
 Multiply original value by a ratio equal to
Multiply original value by a ratio equal to
one
one
 Example
Example
cm
1
.
38
in
1
cm
54
.
2
in
0
.
15
cm
?
in
0
.
15









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

Significant Figures
Significant Figures
 0.0075 m
0.0075 m has 2 significant figures
has 2 significant figures
 The leading zeros are placeholders only
The 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 10-3
3
m
m for 2 significant figures
for 2 significant figures
 10.0 m
10.0 m has 3 significant figures
has 3 significant figures
 The decimal point gives information about the
The decimal point gives information about the
reliability of the measurement
reliability of the measurement
 1500 m
1500 m is ambiguous
is ambiguous
 Use
Use 1.5 x 10
1.5 x 103
3
m
 Use
Use 1.50 x 10
1.50 x 103
3
m
 Use
Use 1.500 x 10
1.500 x 103
3
m

Operations with Significant Figures –
Multiplying or Dividing
Multiplying 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 m
25.57 m x 2.45 m = 62.6 m2
2
 The
The 2.45 m
2.45 m limits your result to 3 significant
limits your result to 3 significant
figures
figures

Adding or Subtracting
Adding 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 cm
135 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 value
decimal value

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
division
division

For adding and subtracting, the
For adding and subtracting, the number of
number of
decimal places
decimal places is the important
is the important
consideration
consideration

For multiplying and dividing, the
For multiplying and dividing, the number of
number of
significant figures
significant figures is the important
is the important
consideration
consideration

Rounding
Rounding
 Last retained digit is increased by 1 if the
Last retained digit is increased by 1 if the
last digit dropped is 5 or above
last 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 number
nearest even number
 Saving rounding until the final result will
Saving rounding until the final result will
help eliminate accumulation of errors
help eliminate accumulation of errors

 Explain the problem with your own words.
Explain the problem with your own words.
 Make a good picture describing the problem
Make 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 tactics
Problem solving tactics


reasonable
reasonable

values for length, mass, and time will help
values for length, mass, and time will help
you test for reasonableness
you test for reasonableness

Chapter 1 introduction of physic for student

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