Physics 518 Agenda for Today Course Introduction General Announcements Structure of the course Scope of the course Begin chapter 1 Course Homepage: http://physicsgbhs.weebly.com/ 1

General Announcements Assignments: Text: Glencoe Science: Physics Principles and Problems Reading Assignment: Chapters 1 Homework will do as Indicated on the Website and on the Board each day. Lectures: (the PowerPoint component) will be posted at the course website Videos: Selected YouTube videos will be availaible on line to help with learning the topcis

Grading Several components: Lecture: Occasional reading quizzes Homework and Classwork (15%) Exams: 40 % Tests 30% Quizzes Class time: Review homework, at most one day per week Cooperative learning exercises Labs: (15%) Mostly worksheets 2

Three main components: Discussion class material Lecture Three main components: Discussion class material Selected topics from text Demonstrations of physical phenomenon Physics is an experimental science Example: Egg Roll Today Interactive exercise with conceptual “Active Learning” problems Critical thinking and problem solving (Almost no memorization required) Act

Course Objectives To begin to understand basic principles (e.g. Newton's Laws) and their consequences (e.g. conservation of momentum, etc.) To solve problems using both quantitative and qualitative applications of these physical principles To develop an intuition of the physical world

Scope of Physics 518 Classical Mechanics: Mechanics: How and why things work. Motion (dynamics), balance (statics), energy, vibrations, some thermodynamics Classical: Not too fast (v << c), c ≡ speed of light Not too small (d >> atom), atoms  10-9 m Most everyday situations can be described in these terms. Path of baseball (or a ping pong ball) Path of rubber ball bouncing against a wall Vibrations of an elastic string (Vibration Demo) (These reflect Newton’s Laws and forces) Properties of matter; a roll of the dice

This Week Position and Time (Chapter 1) What is Physics Scientific Method Vectors Scientific Notation Systems of units Dimensional Analysis Significant digits 1

Physics can also be described as the science of motion. What is Physics…..

The Methods of Science

What is Science? 1. studies the natural world 2. discovers knowledge 3.  discovers nature's "rules" about how things work 4.  only deals with natural phenomena and natural causes               *excludes supernatural

Branches of Science 1.  Life science  (biology, microbiology, botany, evolution) - deals with living things 2.  Earth science (geology, meteorology) - earth, space, rocks, volcanoes, weather 3.  Physical science  (chemistry, physics) - matter, energy, gravity, light, sound

Scientific Method A step by step process where a scientist investigates a question by observing and performing experiments. Step 1 -  State the problem or pose a question Step 2 - Gather information                 (has someone already investigated this?) Step 3 - Form a hypothesis                            --  a possible explanation or answer

Step 4 - Test the hypothesis with an experiment               Experiments have 2 variables Independent variable - what you change                                 Responding variable (dependent) - what you measure If you want to test the affect of fertilizer, you would add fertilizer to a plant (independent variable) and measure how the plant grows (responding variable) A control is something you do nothing to, used to compare your results you will also have a plant that receives no fertilizer

Step 5 - Conclusion Organize data into charts or graphs that can be read by others Step 6 - Draw Conclusions                   Determine if hypothesis is supported or rejected If hypothesis is not supported - modify hypothesis If hypothesis is supported - repeat experiment

Scientific Method

Hypothesis • A possible explanation or solution to the problem (educated guess) • A hypothesis can be tested by – Making observations – conducting experiments, – taking measurements • The experiments and results must be reproducible; that is, other scientists must be able to recreate the experiment and obtain similar data.

• It may be revised or discarded over time. Scientific Theory • Scientific theory is – Based on numerous observations and supported by experimental results – A specific, testable statement about how things happen. – A conclusion that has held up over time and is accepted by most. (Theory of PlateTectonics) – is the best available explanation of why things work as they do. • It may be revised or discarded over time.

Scientific Theory • Most people use the word THEORY to mean uncertainty, guesswork, or a rough idea – “oh…it is just a theory” …??????? • In science, a THEORY has a more specific meaning… – explains facts or phenomena that have been shown to be true by repeated independent tests and experiments.

Scientific Law a rule of nature that sums up related observations to describe a pattern in nature. does not explain WHY these phenomena happen, it simply describes them

A THEORY is an explanation of why something happens A THEORY is an explanation of why something happens.  It comes from many observations and experiments.  It can be changed with new data. Examples:  Germ Theory                   Theory of Evolution A LAW tells you what happens, like a rule of nature.   Examples:  Law of Gravity                   Law of Thermodynamics

Modeling Scientists sometimes use models to help visualize phenomenon.  The globe is a model you are familiar with. Name some other models.....

Quick Review Experiment: an organized procedure for testing a hypothesis...typically has a control and independent and dependent variables. Control: a standard for comparison Independent variable: the factor (or variable) that is changed by the experimenter Dependent variable: the factor (or variable) that responds to change in the independent variable?

Metric System • Created by French scientists in 1798 – International System of Units (SI) – Units of different size related by powers of 10 • In USA, controlled by NIST (National Institute of Standards and Technology www.nist.gov)

• Fundamental or Base Unit: Metric System • Fundamental or Base Unit: – a standard; a specific quantity – only seven (7) needed to describe all of nature

Metric System

Metric System • To convert between SI units, multiply or divide by the appropriate power of 10. • Prefixes are used to change SI units by powers of 10, as shown in the table below.

The Prefixes Most Commonly Used

Conversion Between Units A conversion factor is a multiplier equal to 1. For example, because 1 kg = 1000 g, you can construct the following conversion factors:

Conversion Between Units Choose a conversion factor that will make the units cancel, leaving the answer in the correct units. For example, to convert 1.34 kg of iron ore to grams, do as shown below:

Conversion Between Units How many megahertz is 750 kilohertz? Convert 5021 centimeters to kilometers. How many seconds in a year? Convert the speed 5.30 m/s to km/h (conversion miles to km is (1 Mile = 1.609344 km)

Scientific Notation • Physicists like to measure the very big, the very small and everything in between. • Earth is about 149,000,000,000 meters from the Sun. • Scientific notation expresses a quantity as a number times a power of 10. 1.49×1011 meters = 14.9×1010 meters = .149×1012 meters …. which is correct? • Proper format: M x 10n where1 M < 10

• Format: M x 10n where1 M < 10 Scientific Notation • Mass of Earth 6,000,000,000,000,000,000,000,000 kg = ? • Mass of an electron 0.000,000,000,000,000,000,000,000,000,000,911 kg = ? • Format: M x 10n where1 M < 10

Standard Scientific Notation: A. Moving the decimal point to left exponent is ___________ number is _____ 1 5 616000 = 6.16 x 10 positive Shift ______ to here by ___ places left > ________ decimal pt. implied 5 B. Moving the decimal point to right exponent is ___________ number is _____ 1 -3 0.0070 = 7.0 x 10 negative Shift ______ to here by ___ places right < 3

Ex: Convert to standard scientific notation number scientific notation 43000 0.0290 2012 0.5 80 80. 4.3 x 104 2.90 x 10-2 2.012 x 103 5 x 10-1 8 x 101 8.0 x 101

Measurements • We measure things to know something about them; to describe, to understand • Measurements must be accurate and mean the same to all • include 3 pieces of information – magnitude (how much) – units – uncertainty

Measurements • measurements are not numbers – numbers are obtained by counting or by definition; measurements are obtained by comparing an object with a standard "unit" – numbers are exact; measurements are inexact –mathematics is based on numbers; science is based on measurement

Measurement Significant digits (sig figs) Include all the numbers that can be read directly from the instrument scale plus one doubtful or estimated number. Reflect the precision of the measurement. Significant digits are considered only when calculating with measurements. There is NO uncertainty with counting or exact conversions.

Figures (numbers) are significant if they are: any zeros that are: a. between any _________________ numbers: 509; or b. to the ___________ of a non-zero number AND to the ___________ of the decimal point: 0.00790; or c. between a non-zero number and the __________ _________ : 10. non-zero significant right right decimal point Ex: number # sig. figs. # sig. fig. 5.3 6.6070 202900 3.00 x 108 0.008 40 0.67 40. 2 5 4 3 1 1 2 2

Ex 1: Measure the length of a box: 2 3 4 5 6 L = 4.7 cm = 4.7 ± 0.1 cm last digit is _____________ estimated

Ex 2: Use a “better” ruler: 1 2 3 4 5 6 L = 0.01 cm 4.67 cm = 4.67 ± last digit is ______________ estimated

B. Sig. figs. when multiplying or dividing: answer has the _________ number of sig. figs., in this case: ____ ____ sig. figs. 3 lower 3.73 x 5.7 = 21 2 ____ sig. figs. 2 C. Sig. figs. when adding or subtracting: 3 18.541 +106.6 125.1 ___ decimal places 1 lower answer has the _________ number of ___________________ , in this case: ____ decimal places 1

Measurement • Precision: • Accuracy: –Degree of exactness –Reflects the ability to measure something – Limited by the smallest division on the measurement scale (least count) – Precision of a measurement is generally given as ± 0.1 the smallest division of the instrument • Accuracy: – closeness to a standard

Other Math Stuff

Dy VI. Slope = m = ________ Dx (x2, y2) = (x1, y1) = ( , ) Steps: 1. Draw a best fit line using a __________ Use two points on the line to calculate m: Steps: 1. Draw a best fit line using a __________ Use two points on the line to calculate m: (x2, y2) = ( , ) ruler 8 32 40 30 m = Dy = Dx = ________ = y2 – y1 x2 – x1 20 32 - 5 8 - 1 10 (x1, y1) = ( , ) 1 5 3.9 2 4 6 8

Math in Physics: