Phys-211

Instructor:

Telephone:

Nguyen Quoc Thinh

01685036392

E-Mail: nguyenquocthinh@hus.edu.vn

Office: 213 T1 (temporary)

Office Hours: By appointment.

Textbook:

Physics for scientists and engineers, Serway, 4th edition

World wide web: http://user.hus.edu.vn/nguyenquocthinh

Study

Suggested Study Procedure

1. Read the assigned topics/materials before coming to

the class/lab.

2. Attend the class, take good notes, and actively

participate in all the activities in the class.

3. Reread the topics/materials.

4. Doing lots of homework problems is the best way to

do well in the class. As you do each problem, think of

what strategy you are using to solve the problem.

Evaluation

Lecture and exercise section grades are combined..

Assignments

Midterm Exam

Exam

20%

30%

50%

The Branches of Physics

Physics

Physics attempts to use a small number of basic

concepts, equations,

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.

Theories and Experiments

The goal of physics is to develop theories

based on experiments

A theory is a “guess” expressed

mathematically, about how a system works

The theory makes predictions about how a

system should work

Experiments check the theories’ predictions

Every theory is a work in progress

Chapter 1

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

the scientific method.

Chapter 1

Models

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 1

Hypotheses

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.

Chapter 1

Hypotheses, continued

Galileo modeled the behavior of falling

objects in order to develop a hypothesis

about how objects fall.

If heavier objects fell

faster than slower

ones,would two bricks of

different masses tied

together fall slower (b) or

faster (c) than the heavy

brick alone (a)? Because

of this contradiction,

Galileo hypothesized

instead that all objects fall

at the same rate, as in

(d).

Chapter 1

Controlled 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.

Units

To communicate the result of a

measurement for a quantity, a unit

must be defined

Defining units allows everyone to relate

to the same fundamental amount

Chapter 1

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).

Systems of Measurement

Standardized systems

agreed upon by some authority, usually a

governmental body

SI -- Système International

agreed to in 1960 by an international committee

main system used in this course

also called mks for the first letters in the units of

the fundamental quantities

Systems of Measurements,

cont

cgs – Gaussian system

named for the first letters of the units it

uses for fundamental quantities

(centimetre, gram, second)

US Customary

everyday units

often uses weight, in pounds, instead of

mass as a fundamental quantity

Length

Units

SI – meter, m

cgs – centimeter, cm

US Customary – foot, ft

Defined in terms of a meter – the

distance traveled by light in a vacuum

during a given time

Mass

Units

SI – kilogram, kg

cgs – gram, g

USC – slug, slug

Defined in terms of kilogram, based on

a specific cylinder kept at the

International Bureau of Weights and

Measures

Mass

The SI unit for mass is the

kilogram.

A kilogram is defined as the

mass of a special platinumiridium alloy cylinder kept at the

International Bureau of Weights

and Measures in France.

Time

Units

seconds, s in all three systems

9,192,631,700 times the period of

oscillation of radiation from the cesium

atom.

Fundamental Quantities and

Their Dimension

Length [L]

Mass [M]

Time [T]

other physical quantities can be

constructed from these three

Chapter 1

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.

Dimensional Analysis

Technique to check the correctness of

an equation

Dimensions (length, mass, time,

combinations) can be treated as

algebraic quantities

add, subtract, multiply, divide

Both sides of equation must have the

same dimensions

Dimensional Analysis, cont.

Cannot give numerical factors: this is

its limitation

Dimensions of some common quantities

Example 1

The following equation was given by a student during an

examination:

v = v 0 + at

2

Do a dimensional analysis and explain why the equation

can’t be correct.

ν has dimensions

L

T

a has dimensions

L

2

T

t has dimension

T

Example 2

Newton’s law of universal gravitation is represented

by

F

Mm

= G

2

r

where F is the gravitational force, M and m are

masses, and r is a length. Force has the SI units kg

· m/s2. What are the SI units of the proportionality

constant G?

Instructor:

Telephone:

Nguyen Quoc Thinh

01685036392

E-Mail: nguyenquocthinh@hus.edu.vn

Office: 213 T1 (temporary)

Office Hours: By appointment.

Textbook:

Physics for scientists and engineers, Serway, 4th edition

World wide web: http://user.hus.edu.vn/nguyenquocthinh

Study

Suggested Study Procedure

1. Read the assigned topics/materials before coming to

the class/lab.

2. Attend the class, take good notes, and actively

participate in all the activities in the class.

3. Reread the topics/materials.

4. Doing lots of homework problems is the best way to

do well in the class. As you do each problem, think of

what strategy you are using to solve the problem.

Evaluation

Lecture and exercise section grades are combined..

Assignments

Midterm Exam

Exam

20%

30%

50%

The Branches of Physics

Physics

Physics attempts to use a small number of basic

concepts, equations,

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.

Theories and Experiments

The goal of physics is to develop theories

based on experiments

A theory is a “guess” expressed

mathematically, about how a system works

The theory makes predictions about how a

system should work

Experiments check the theories’ predictions

Every theory is a work in progress

Chapter 1

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

the scientific method.

Chapter 1

Models

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 1

Hypotheses

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.

Chapter 1

Hypotheses, continued

Galileo modeled the behavior of falling

objects in order to develop a hypothesis

about how objects fall.

If heavier objects fell

faster than slower

ones,would two bricks of

different masses tied

together fall slower (b) or

faster (c) than the heavy

brick alone (a)? Because

of this contradiction,

Galileo hypothesized

instead that all objects fall

at the same rate, as in

(d).

Chapter 1

Controlled 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.

Units

To communicate the result of a

measurement for a quantity, a unit

must be defined

Defining units allows everyone to relate

to the same fundamental amount

Chapter 1

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).

Systems of Measurement

Standardized systems

agreed upon by some authority, usually a

governmental body

SI -- Système International

agreed to in 1960 by an international committee

main system used in this course

also called mks for the first letters in the units of

the fundamental quantities

Systems of Measurements,

cont

cgs – Gaussian system

named for the first letters of the units it

uses for fundamental quantities

(centimetre, gram, second)

US Customary

everyday units

often uses weight, in pounds, instead of

mass as a fundamental quantity

Length

Units

SI – meter, m

cgs – centimeter, cm

US Customary – foot, ft

Defined in terms of a meter – the

distance traveled by light in a vacuum

during a given time

Mass

Units

SI – kilogram, kg

cgs – gram, g

USC – slug, slug

Defined in terms of kilogram, based on

a specific cylinder kept at the

International Bureau of Weights and

Measures

Mass

The SI unit for mass is the

kilogram.

A kilogram is defined as the

mass of a special platinumiridium alloy cylinder kept at the

International Bureau of Weights

and Measures in France.

Time

Units

seconds, s in all three systems

9,192,631,700 times the period of

oscillation of radiation from the cesium

atom.

Fundamental Quantities and

Their Dimension

Length [L]

Mass [M]

Time [T]

other physical quantities can be

constructed from these three

Chapter 1

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.

Dimensional Analysis

Technique to check the correctness of

an equation

Dimensions (length, mass, time,

combinations) can be treated as

algebraic quantities

add, subtract, multiply, divide

Both sides of equation must have the

same dimensions

Dimensional Analysis, cont.

Cannot give numerical factors: this is

its limitation

Dimensions of some common quantities

Example 1

The following equation was given by a student during an

examination:

v = v 0 + at

2

Do a dimensional analysis and explain why the equation

can’t be correct.

ν has dimensions

L

T

a has dimensions

L

2

T

t has dimension

T

Example 2

Newton’s law of universal gravitation is represented

by

F

Mm

= G

2

r

where F is the gravitational force, M and m are

masses, and r is a length. Force has the SI units kg

· m/s2. What are the SI units of the proportionality

constant G?

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