1. College Physics
Chapter 1
Introduction

2. Physics 2010/2011 Instructor: Allen Hunley
Telephone: (931) (office)
Office Hours: By appointment. (I am an adjunct member so I do not have an office at APSU.)
Textbook: College Physics (7th Edition)
by Serway & Faughn
Thomson Books/Cole (2006)

3. World Wide Web
Course
Web Address:
Textbook
Web Address:
(Physics Now Web Site, free if you purchased a new edition textbook)

4. 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. Work the assigned problems starting the first day that they are assigned - you will require time for this material to "sink in"!
5. Ask questions in the interim.
6. Use a three-hole binder for the course so that you can keep all the materials (notes, homework assignments, answer sheets, exams, labs, etc.) in it. This will help you to find all the necessary materials when you prepare for your exams.

5. Evaluation
Lecture and lab grades are combined. You will receive the same letter grade for the lecture course as for the lab course.
In summary, the distribution of credits among the various assignments is as following:
Guide to letter grades is:
Homework Assignments 15 points A =
Lab Activities points B = 80 – 89
Exams points C = 70 – 79
Final Exam points D = 60 – 69
Total points F =

6. Laboratory
Laboratory activities are highly valued in physics and are incorporated into our classes. These activities may consist of traditional hands-on experiments or computer simulations. You will be working in groups with 2-3 students in each group. The grade is based entirely on the lab write-ups you turn in. These activities contribute 20% of your grade.

7. The aims of the class
On of the aims of this class is to teach you to think in a physics way.
As you see each concept, try to get a mental picture of how it works.
You will learn as much about how to solve problems as you do about the laws of physics themselves.
So you will need to approach this class differently from many of the other classes you are taking. Simply memorizing solutions will not help.
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.

8. The Branches of Physics

9. Physics
Physics attempts to use a small number of basic concepts, 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.

10. 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

11. The Scientific Method Chapter 1
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.

12. Models Chapter 1 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.

13. Hypotheses Chapter 1 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.

14. 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).

15. Controlled Experiments
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.

16. 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

17. Numbers as Measurements
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).

18. Systems of Measurement
Standardized systems
agreed upon by some authority, usually a governmental body
SI -- Systéme International
agreed to in 1960 by an international committee
main system used in this text
also called mks for the first letters in the units of the fundamental quantities

19. Systems of Measurements, cont
cgs – Gaussian system
named for the first letters of the units it uses for fundamental quantities
US Customary
everyday units
often uses weight, in pounds, instead of mass as a fundamental quantity

20. 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

21. 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

22. The SI unit for mass is the kilogram.
A kilogram is defined as the mass of a special platinum-iridium alloy cylinder kept at the International Bureau of Weights and Measures in France.

23. Time
Units
seconds, s in all three systems
9,192,631,700 times the period of oscillation of radiation from the cesium atom.

24. Fundamental Quantities and Their Dimension
Length [L]
Mass [M]
Time [T]
other physical quantities can be constructed from these three

25. Dimensions and Units Chapter 1
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.

26. 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

27. Dimensional Analysis, cont.
Cannot give numerical factors: this is its limitation
Dimensions of some common quantities are listed in Table 1.5

28. Example 1
The following equation was given by a student during an examination:
Do a dimensional analysis and explain why the equation can’t be correct.
ν has dimensions a has dimensions t has dimension

29. Example 2 Newton’s law of universal gravitation is represented by
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?

30. Prefixes Prefixes correspond to powers of 10
Each prefix has a specific name
Each prefix has a specific abbreviation
See table 1.4

31. Chapter 1
SI Prefixes
In SI, units are combined with prefixes that symbolize certain powers of 10. The most common prefixes and their symbols are shown in the table.

32. Conversions
When units are not consistent, you may need to convert to appropriate ones
Units can be treated like algebraic quantities that can “cancel” each other
See the inside of the front cover for an extensive list of conversion factors
Example:

33. Sample Problem Given: mass = 2.0 fg Chapter 1
A typical bacterium has a mass of about 2.0 fg. Express
this measurement in terms of grams and kilograms.
Given:
mass = 2.0 fg
Unknown:
mass = ? g mass = ? kg

34. Sample Problem, continued
Chapter 1
Sample Problem, continued
Build conversion factors from the relationships given in
Table 3 of the textbook. Two possibilities are:
Only the first one will cancel the units of femtograms to
give units of grams.

35. Sample Problem, continued
Chapter 1
Sample Problem, continued
Take the previous answer, and use a similar process to
cancel the units of grams to give units of kilograms.

36. Converting Units Example 3
Convert the following:
25m to cm
345m to Km
550cm to Km
0.3 m/s to Km/hr

37. Mathematics and Physics
Chapter 1
Mathematics and Physics
Tables, graphs, and equations can make data easier to understand.
For example, consider an experiment to test Galileo’s hypothesis that all objects fall at the same rate in the absence of air resistance.
In this experiment, a table-tennis ball and a golf ball are dropped in a vacuum.
The results are recorded as a set of numbers corresponding to the times of the fall and the distance each ball falls.
A convenient way to organize the data is to form a table, as shown on the next slide.

38. Data from Dropped-Ball Experiment
Chapter 1
Data from Dropped-Ball Experiment
A clear trend can be seen in the data. The more time that
passes after each ball is dropped, the farther the ball falls.

39. Graph from Dropped-Ball Experiment
Chapter 1
Graph from Dropped-Ball Experiment
One method for analyzing the data is to construct a graph of the distance the balls have fallen versus the elapsed time since they were released. a
The shape of the graph provides information about the relationship between time and distance.

40. Equation from Dropped-Ball Experiment
Chapter 1
Equation from Dropped-Ball Experiment
We can use the following equation to describe the relationship between the variables in the dropped-ball experiment:
(change in position in meters) = 4.9  (time in seconds)2
With symbols, the word equation above can be written as follows:
Dy = 4.9(Dt)2
The Greek letter D (delta) means “change in.” The abbreviation Dy indicates the vertical change in a ball’s position from its starting point, and Dt indicates the time elapsed.
This equation allows you to reproduce the graph and make predictions about the change in position for any time.

41. Coordinate Systems Used to describe the position of a point in space
Coordinate system consists of
a fixed reference point called the origin
specific axes with scales and labels
instructions on how to label a point relative to the origin and the axes
Cartesian
Plane polar

42. Cartesian coordinate system
Also called rectangular coordinate system
x- and y- axes
Points are labeled (x,y)

43. Plane polar coordinate system
Origin and reference line are noted
Point is distance r from the origin in the direction of angle , ccw from reference line
Points are labeled (r,)

44. Trigonometry Review

45. More Trigonometry Pythagorean Theorem
To find an angle, you need the inverse trig function
for example,
Be sure your calculator is set appropriately for degrees or radians

46. Problem Solving Strategy

47. Problem Solving Strategy
Read the problem
Identify the nature of the problem
Draw a diagram
Some types of problems require very specific types of diagrams

48. Problem Solving cont. Label the physical quantities
Can label on the diagram
Use letters that remind you of the quantity
Many quantities have specific letters
Choose a coordinate system and label it
Identify principles and list data
Identify the principle involved
List the data (given information)
Indicate the unknown (what you are looking for)

49. Problem Solving, cont. Choose equation(s)
Based on the principle, choose an equation or set of equations to apply to the problem
Substitute into the equation(s)
Solve for the unknown quantity
Substitute the data into the equation
Obtain a result
Include units

50. Problem Solving, final Check the answer Do the units match?
Are the units correct for the quantity being found?
Does the answer seem reasonable?
Check order of magnitude
Are signs appropriate and meaningful?

51. Problem Solving Summary
Equations are the tools of physics
Understand what the equations mean and how to use them
Carry through the algebra as far as possible
Substitute numbers at the end
Be organized

52. Example 4
A certain corner of a room is selected as the origin of a rectangular coordinate system. If a fly is crawling on an adjacent wall at a point having coordinates (2.0, 1.0), where the units are meters, what is the distance of the fly from the corner of the room?

53. Example 5
For the triangle shown in Figure P1.39, what are (a) the length of the unknown side, (b) the tangent of θ, and (c) the sine of φ?

54. Example 6
A high fountain of water is located at the center of a circular pool as shown in Figure P1.41. Not wishing to get his feet wet, a student walks around the pool and measures its circumference to be 15.0 m. Next, the student stands at the edge of the pool and uses a protractor to gauge the angle of elevation at the bottom of the fountain to be 55.0°. How high is the fountain?

55. Example 7
A surveyor measures the distance across a straight river by the following method: Starting directly across from a tree on the opposite bank, he walks 100 m along the riverbank to establish a baseline. Then he sights across to the tree. The angle from his baseline to the tree is 35.0°. How wide is the river?

56. Accuracy and Precision
Chapter 1
Accuracy and Precision
Accuracy is a description of how close a measurement is to the correct or accepted value of the quantity measured.
Precision is the degree of exactness of a measurement.
A numeric measure of confidence in a measurement or result is known as uncertainty. A lower uncertainty indicates greater confidence.

57. Uncertainty in Measurements
There is uncertainty in every measurement, this uncertainty carries over through the calculations
need a technique to account for this uncertainty
We will use rules for significant figures to approximate the uncertainty in results of calculations

58. Significant Figures A significant figure is one that is reliably known
All non-zero digits are significant
Zeros are significant when
between other non-zero digits
after the decimal point and another significant figure
can be clarified by using scientific notation

59. Rules for Determining Significant Zeros
Chapter 1
Rules for Determining Significant Zeros

60. Example 8 How many significant digits are in each of the following:
) 0.007
) 1.09
) 100 )

61. Operations with Significant Figures
When adding or subtracting, round the result to the smallest number of decimal places of any term in the sum
If the last digit to be dropped is less than 5, drop the digit
If the last digit dropped is greater than or equal to 5, raise the last retained digit by 1

62. Operations with Significant Figures, cont.
When multiplying or dividing two or more quantities, the number of significant figures in the final result is the same as the number of significant figures in the least accurate of the factors being combined

63. Rules for Calculating with Significant Figures

64. Example 9
A fisherman catches two striped bass. The smaller of the two has a measured length of cm (two decimal places, four significant figures), and the larger fish has a measured length of cm (one decimal place, four significant figures). What is the total length of fish caught for the day?

65. Example 10
Using your calculator, find, in scientific notation with appropriate rounding,
the value of (2.437 × 104)( × 109)/(5.37 × 104)
and
(b) ( × 102)(27.01 × 104)/(1 234 × 106).

66. Derived Units Derived units are combinations of the base units (mks).
Area is measured in m2
Volume is measured in m3
Speed is measured in m/s