Lecture 1 - Physics and Astronomy | Physics and Astronomy

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Ch 1 Introduction Physics andMeasurement Estimating Chapter 1 Outline1 The Nature of Science2 Models Theories Laws.
3 Measurement UncertaintySignificant Figures4 Units Standards the SI System5 Converting Units6 Order of Magnitude Rapid Estimating.
7 Dimensions Dimensional AnalysisThe most basic of all sciences Physics The Parent of all sciences Physics The study of the behaviorof and the structure of matter and.
energy and of the interactionbetween matter and energy Sub Areas of Physics This course 1408 Physics of 16th 17th Centuries Motion MECHANICS most of our time .
Fluids Waves Next course 2401 Physics of 18th 19th Centuries Electricity magnetism Light optics Advanced courses Physics of the 20th Century .
Relativity atomic structure condensed matter nuclear physics These are the most interesting themost relevant to modern technology Mechanics.
Classical Mechanics Mechanics Classical Mechanics Classical Physics Classical Before the 20th CenturyThe foundation of pure applied.
macroscopic physics engineering Newton s Laws Boltzmann s Statistical Mechanics Thermodynamics Describe most of macroscopic world However at high speeds v c we needSpecial Relativity Early 20th Century 1905 .
Also for small sizes atomic smaller we needQuantum Mechanics 1900 through 1930 Classical Mechanics 17th 18th Centuries Still useful today Classical Mechanics.
The physics in this course is limited to macroscopic objectsmoving at speeds v much much smaller than the speed of lightc 3 108 m s As long as v c our discussion will be valid So we will workexclusively in the.
gray region in the Mechanics 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 howdo objects move Physics General Discussion.
The Goal of Physics all of science To quantitatively qualitatively describe the world around us Physics IS NOT merely a collection offacts formulas Physics IS a creative activity .
Physics Observation Explanation Requires IMAGINATION Physics Its Relation to Other FieldsThe Parent of all Sciences The foundation for connected to ALL.
branches of science and engineering Also useful in everyday life and in MANYprofessions Chemistry Life Sciences Medicine also .
Architecture Engineering Various technological fields Physics Principles are used in many practicalapplications including construction .
Communication between Architects Engineers is essential if disaster is to be avoided The Nature of Science 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.
Experiments Observations Will tell if predictions are accurate No theory can be absolutely verified But a theory CAN be proven false A Quantitative mathematical Description.
of experimental observations Not just WHAT is observed but WHY it isobserved as it is and HOW it works the way it does Tests of Theories Experimental observations .
More experiments more observation Predictions Made before observations experiments 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 abouthow nature behaves Must be verified by.
many many experiments Only a few laws Not comparable to laws ofgovernment 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 old theory Aristotle Believed that objects would return to restonce put in motion .
Galileo Realized that an object put in motion wouldstay in motion until some force stopped it Newton Developed his Laws of Motion to put Galileo sobservations into mathematical language .
Measurement Uncertainty Significant FiguresNo measurement is exact there is alwayssome uncertainty due to limited instrumentaccuracy difficulty reading results .
The photograph to theleft illustrates this itwould be difficult tomeasure the width ofthis 2 4 to better than a.
millimeter 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 uncertaintyin the final result This is known as experimental error .
It is common to state this precision when Consider a simple measurement of thewidth of a board Find 23 2 cm However measurement is only accurate to0 1 cm estimated .
We write the width as 23 2 0 1 cm 0 1 cm Experimental uncertainty Percent Uncertainty 0 1 23 2 100 0 4 .
Significant FiguresSignificant Figures sig figs The number of significant figures is thenumber of reliably known digits in a number It is usually possible to tell the number of significant.
figures by the way the number is written 23 21 cm has 4 significant figures0 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 Calculations Involving Several NumbersWhen multiplying or dividing numbers The number of sig figs in the result the.
same number of sig figs as the number usedin the calculation with the fewest sig figs When adding or subtracting numbers The answer is no more accurate thanthe least accurate number used .
Example Not to scale Area of a board dimensions 11 3 cm 6 8 cm Area 11 3 6 8 76 84 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 answer 2 Round off 76 84 keep only 2 sig figs Reliable answer for area 77 cm2.
Sig Figs General Rule The final result ofmultiplication or division should haveonly as many sig figs as the numberwith least sig figs in the calculation .
All digits on your calculator areNOT significant Calculators will not give you theright number of significant figures they usually give too many but.
sometimes give too few especiallyif there are trailing zeroes after adecimal point The top calculator shows the result The bottom calculator shows the.
2 5 3 2 Conceptual Example Significant Figures Using a protractor you measure an angle of 30 a How many significant figures should you quote in thismeasurement .
b Use a calculator to find the cosine of the angle you a Precision 1 not 0 1 So 2 sig figs angle is30 not 30 0 b Calculator cos 30 .
0 866025403 But angleprecision is 2 sig figs soanswer should also be 2 sigfigs So cos 30 0 87 Powers of 10 Scientific Notation .
READ Appendix B 1 It is common to express very large or verysmall numbers using powers of 10 notation 39 600 3 96 104 moved decimal 4 places to left .
0 0021 2 1 10 3 moved decimal 3 places to right PLEASE USE SCIENTIFIC NOTATION Powers of 10 Scientific Notation PLEASE USE SCIENTIFIC NOTATION .
This is more than a request I m making it arequirement I want to see powers of 10notation on exams For large numbers like 39 600 .
I want to see 3 96 104 NOT 39 600 For small numbers like 0 0021 I want to see 2 1 10 3 NOT 0 0021 On the exams you will lose pointsif you don t do this .
Accuracy vs Precision Accuracy is how close a measurementcomes to the accepted true value Precision is the repeatability of themeasurement using the same instrument.
getting the same result It is possible to be accurate withoutbeing precise and to be precisewithout being accurate .
Physics: The “Parent” of all sciences! Physics = The study of the behavior of and the structure of matter and energy and of the interaction between matter and energy. Sub Areas of Physics This course (1408, Physics of 16th & 17th Centuries): Motion (MECHANICS) (most of our time!)

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