1. Chapter 1: Introduction

2. Physics The most basic of all sciences!
The “Parent” of all sciences!
The study of the behavior & the
structure of matter & energy & of the interaction between them.

3. The Purpose of Physics
What does the word physics mean?
A connection with natural philosophy.
It is organized around a collection of natural laws
It tries to predict how “the world works.”
It tries to understand why “the world works the way it does.”

4. What is Physics?
Physics is the science of matter & energy & interactions between them
Matter & Energy are fundamental to all areas of science.
Physics is a foundational subject
The principles of Physics form the basis of understanding other sciences.
Physics allows us to understand things from very large to very small.

5. Physicists. What is Physics?
It is the study of the natural or material world & phenomena
The meaning of “physics” comes
from the Greek word for nature
Historically, it was “Natural Philosophy”
It is the oldest science
Historically, all scientists were
Physicists.

6. (Newton’s Laws of Motion!)
Studying Physics
The goal is to predict & understand how the universe works
It is organized around physical laws
What do the laws say?
(Newton’s Laws of Motion!)
How can we apply the laws to new situations?
Mathematics
The laws of physics are generally expressed mathematically

7. Sir Isaac Newton Sir Isaac Newton
Mechanics is the main
physics area studied
in this course.
The Laws of Mechanics
were developed by
Sir Isaac Newton
Newton’s Laws of Motion
Apply to a wide variety of macroscopic objects

8. The next course: Physics 1404
Sub Areas of Physics
This course: Physics 1403
Physics of the 16th & 17th Centuries:
Motion (MECHANICS) (most of our time!)
Fluids & Waves
The next course: Physics 1404
Physics of the 18th & 19th Centuries:
Electricity & Magnetism
Light & Optics

9. Physics of the 20th & 21st Centuries!
Sub Areas of Physics
Advanced courses
Physics of the 20th & 21st Centuries!
Relativity, Quantum Mechanics, Atomic Structure, Condensed Matter, Nuclear Physics, Particle Physics, Astrophysics, Cosmology,….
These are the most interesting & the most relevant to modern technology!

10. “Classical” Mechanics

11. Mechanics: “Classical” Mechanics “Classical” Physics:
“Classical”   Before the 20th Century
The foundation of pure & applied
macroscopic physics & engineering!
Newton’s Laws of Motion
+ Boltzmann’s Statistical Mechanics
(+ Thermodynamics)
+ Maxwell’s Electromagnetism:
 Describe most of macroscopic world!

12. “Classical” Mechanics:
But,
For objects at high speeds (v ~ c) we need Special Relativity: (c = speed of light)
(Early 20th Century: 1905)
For objects with small sizes (atomic & smaller) we need Quantum Mechanics:
(1900 through ~ 1935)
Our focus will be on
“Classical” Mechanics:
(17th & 18th Centuries)
Still useful today!

13. “Classical” Mechanics
The physics in this course will be limited to macroscopic objects moving at speeds v much, much smaller than the speed of light c = 3  108 m/s. As long as v << c, our discussion will be valid.
So, we will work
exclusively in
the gray region
in the figure.

14. “Mechanics” “Given the forces, how do objects move”?
The science of HOW objects move (behave) under given forces.
(Usually) Does not deal with the sources of forces.
Answers the question:
“Given the forces, how
do objects move”?

15. Physics: General Discussion
The Goal of Physics (& all of science) is to quantitatively & qualitatively
describe the “world around us”.
Physics IS NOT merely a collection of facts and formulas!
Physics IS a creative activity!
Physics  Observation  Explanation.
Requires Research &
IMAGINATION!!

16. Physics & Its Relation to Other Fields
The “Parent” of all Sciences!
The foundation for & connected to ALL branches of science & engineering.
Also useful in everyday life & in MANY professions
Chemistry
Life Sciences (Medicine also!!)
Architecture
Engineering
Various technological fields

17. Physics Principles are used in many practical applications, including construction. Communication between Architects & Engineers is essential to avoid disaster!!!
Figure 1-1. Caption: (a) This Roman aqueduct was built 2000 years ago and still stands. (b) The Hartford Civic Center collapsed in 1978, just two years after it was built.

18. The Nature of Science Experiments & Observations: Theories:
Physics is an EXPERIMENTAL science!
Experiments & Observations:
Important first steps toward scientific theory.
It requires imagination to tell what is important.
Theories:
Created to explain experiments & observations. Will also make predictions
Will tell if predictions are accurate.
No theory can be absolutely verified
But a theory CAN be proven false!!!

19. Theory Tests of Theories: Experimental observations: Predictions:
A Quantitative (Mathematical) Description of experimental observations.
Not just WHAT is observed but WHY it’s observed as it is & HOW it works the way it does.
Tests of Theories:
Experimental observations:
More experiments, more observations.
Predictions:
Made before observations & experiments.

20. Not comparable to laws of government!
Model, Theory, Law
Model: Analogy of a physical phenomenon to something we are familiar with.
Theory: More detailed than a model. Puts the model into mathematical language.
Law: A concise & general statement about how nature behaves. Must be verified by many, many experiments! Only a few laws.
Not comparable to laws of government!

21. How does a new theory get accepted?
It’s Predictions:
Agree better with data than those of an old theory
It Explains:
A greater range of phenomena than the old theory
Example
Aristotle: Believed that objects would return to rest once put in motion.) (He was 100% wrong about everything he said about physics!)
Galileo: Realized that an object put in motion would stay in motion until some force stopped it.
Newton: Developed his Laws of Motion to put Galileo’s observations into mathematical language.

22. Measurement & Uncertainty; Significant Figures
No measurement is exact; there is always some uncertainty due to limited instrument accuracy & difficulty reading the results.
The photograph illustrates this – it would be difficult to measure the width of this 24 to better than a
millimeter.

23. Measurement & Uncertainty
Physics is an EXPERIMENTAL science!
It finds relations between physical quantities.
It expresses those relations in the language of mathematics. (LAWS & THEORIES)
Experiments are NEVER 100% accurate.
There is always an uncertainty
in the final result.
This is known as Experimental Error.
It is common to state this precision (when it is known).

24.  0.1 cm  Experimental uncertainty
Consider a simple measurement of the width of a board. Find 23.2 cm.
However, measurement is only accurate to 0.1 cm (estimated).
Write the width as (23.2  0.1) cm
 0.1 cm  Experimental uncertainty
Percent Uncertainty:
 (0.1/23.2)  100   0.4%

25. The number the number of reliably (initial zeroes don’t count)
Significant Figures
Significant Figures (“sig figs”) 
The number the number of reliably
known digits in a number.
Its usually possible to tell the number of significant figures by how the number is written:
23.21 cm has 4 significant figures
0.062 cm has 2 significant figures
(initial zeroes don’t count)
80 km is ambiguous: It could have 1 or 2 significant figures. If it has 3, it should be written 80.0 km

26. The answer is no more accurate than the least accurate number used.
Sig Figs in Calculations With Numbers
Multiplying or dividing numbers:
The number of sig figs in the result  the same number of sig figs as the number with the fewest sig figs that is used in the calculation.
Adding or subtracting numbers:
The answer is no more accurate than the least accurate number used.

27. 76.84 has too many sig figs! Example Reliable answer for area = 77 cm2
(Not to scale!)
Area of a board:
dimensions 11.3 cm  6.8 cm
Area = (11.3)  (6.8) = cm2
11.3 has 3 sig figs , 6.8 has 2 sig figs
76.84 has too many sig figs!
Proper number of sig figs in the answer = 2
So, round off & keep only 2 sig figs
Reliable answer for area = 77 cm2

28. All digits on your calculator are NOT significant!!
Sig Figs
General Rule: The final result of multiplication or division should have only as many sig figs as the number with least sig figs in the calculation.
NOTE!!!!
All digits on your calculator are NOT significant!!

29. 2.0 / 3.0 2.5  3.2. Calculators will not give you the
right number of sig figs. They
usually give too many, but
sometimes give too few
(especially if there are trailing
zeroes after a decimal point).
The top calculator shows the
result of
2.0 / 3.0
The bottom calculator shows the
2.5  3.2.

30. Example: Significant Figures
Using a protractor, you measure an angle of 30°.
(a) How many significant figures should you quote
in this measurement?
(b) Use a calculator to find the cosine of the angle you
measured.
(a) Precision ~ 1° (not 0.1°).
So 2 sig figs & angle is
30° (not 30.0°).
(b) Calculator: cos(30°) =
But angle
precision is 2 sig figs so
answer should also be 2
sig figs. So cos(30°) = 0.87

31. Powers of 10 (Scientific Notation)
READ Appendix B.3
It is common to express very large or very small numbers using powers of 10 notation.
Examples:
39,600 = 3.96  104 (moved the decimal 4 places to the left)
= 2.1  10-3 (moved the decimal 3 places to the right)
PLEASE USE SCIENTIFIC NOTATION!!

32. USE SCIENTIFIC NOTATION!!
This is more than a request!! I’m making it a requirement!!
When appropriate, I want to see powers of 10 notation on exams!!
For large numbers, like 39,600,
I want to see 3.96  104 & NOT 39,600!!
For small numbers, like ,
I want to see 2.1  10-3 & NOT !!
On exams, you will lose points if you don’t do this!!

33. Accuracy vs. Precision
Accuracy is how close a measurement comes to the accepted (true) value.
Precision is the repeatability of the measurement using the same instrument & getting the same result!
It is possible to be accurate without being precise and to be precise without being accurate!

34. Some General Comments on Physics Problem Solving
Problem Solving is the process of applying a general physical law to a particular case
Problem Solving is an essential part of physics
Problem Solving takes a lot of practice!
The only way to learn physics is
to DO physics by solving HUGE numbers of problems!

35. Types of Problems
In this course, we’ll solve various types of problems:
Quantitative Problems: Given some numerical information, use calculations to find some physical quantity.
Concept Checks: Test your general understanding of a law & its applications

36. Reasoning & Relationship Problems
Identify what important information might be “missing”.
Successfully dealing with these types of problems is essential to gaining a thorough understanding of physics

37. Problem Solving Strategies
Recognize the key physics principles needed.
You need a conceptual understanding of the physics laws, how they are applied, & how they are interrelated
Sketch the Problem!
Show the given information
Generally this includes a coordinate system

38. Problem Solving Strategies
Identify the important relationships
Use the given information & the unknown quantities to determine what laws apply
This may involve several substeps
Solve for the unknown quantities
Be careful to do the math correctly!
Check your calculations!
What do your answers mean?
Do your answers agree with common sense?

39. Problem Solving Strategies
Most importantly,
Think about your answers! Are they reasonable?
Use common sense!!