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1、IntroductionChapter 1Chapter 1Getting prepared!Chapter 1.IntroductionMeasurement,Models,Measurement,Models,Theories and LawsTheories and Laws Vector and Scalar Vector and ScalarIntroductionChapter 1Chapter 11-1 Models,theories,and laws(P3)Model:is a kind of mental image of the phenomena in terms of
2、something are familiar with.Theory:is broader,more detailed,and attempts to solve a set of phenomena.Law:are general statements about how nature behaves.The statement takes the form of a relationship or equation(方方 程程)between quantities(量量).IntroductionChapter 1Chapter 11-2 Measurement and Uncertain
3、ty;Significant Figures(P3-5)Physics is based on measurement of physical quantities (物理量物理量).P3Significant Figures(有有效效数数字字):The number of reliably known digits in a number is called the number of significant figures.P4IntroductionChapter 1Chapter 1Mass of the Earth:5,980,000,000,000,000,000,000,000k
4、gor 5.98x1024kgDiameter of proton（质子）质子）:0.000000000000001mor 10-15m(or 1 E-15 on computers)The advantage is that it allows the number of significant figures to be clearly expressed.Scientific notation(科学科学记记数法数法(p4)Write numbers in“powers of ten”.IntroductionChapter 1Chapter 11-4 Units,Standards,an
5、d the SI System(P5-7)Unit(单单位位):We measure each physical quantity in its own units(单单位位)by comparison with a standard.P5SI System(国国际际单单位位制制):There are so many physical quantities that it is a problem to organize them.Fortunately,they are not all independent（独立）独立）.P7IntroductionChapter 1Chapter 1In
6、 1971,the 14th General Conference on Weights and Measures,The SI(International System)was adopted.It is based on meter,second and kilogram.It is also called Metric System(公公制制）or MKS system.Many SI(System International)derived units are defined in terms of these base units,such as:1 watt=1 W=1 kg m2
7、/s3 The second metric system is CGS(P7),in which the centimeter,gram,and second are the standard units of length,mass and time.IntroductionChapter 1Chapter 1exa E 1018 peta P 1015tera T 1012giga G 109Mega M 106kilo k 103Hecto h 102deka da 101deci d 10-1centi c 10-2milli m 10-3Micro 10-6nano n 10-9pi
8、co p 10-12femto f 10-15 atto a 10-18Shorthand and some commonly used units(P7)IntroductionChapter 1Chapter 1Base quantities(基本量基本量):length,time,mass.Base units(基本单位基本单位):meter,second,kilogram.Derivative quantities(导导 出出 量量):The quantities derived from base quantities such as：velocity，acceleration.De
9、rivative units(导导 出出 单单 位位):The units derived from base units such as：m/s m/s2.Consistent set of unitsIntroductionChapter 1Chapter 1 One meter is the length of path traveled by light in a vacuum during a time interval（间间隔隔）of 1/299792458 of a second.P5 One second is the time taken by 9192631770 osci
10、llations(振振动动)of the light emitted by a cesium（铯）铯）-133 atom.One kilogram is defined in terms of(根据、按照）根据、按照）a particular platinum-iridium（铂铱）铂铱）cylinder（柱柱体）体）kept near Paris,France.For measurements on an atomic scale,the atomic mass unit,defined in terms of the atom carbon-12,is usually used.1u=1.
11、6605402x10-27 kg（1）Length（长度长度P5）:（2）Time（时间时间P6）:（3）Mass（质量质量P6）:IntroductionChapter 1Chapter 1Some scalars are always positive,whereas others such as electric charge(电电荷荷)can be positive or negative.Scalar(标标量量):A ordinary algebraic(代代数数的的)quantity that has no direction.(mass,time,temperature,)Vec
12、tor(矢矢量量):A quantity that has both direction(方方向向)and magnitude(大大小小)(displacement 位位移移,velocity 速度速度,acceleration 加速度加速度,force力力).3-1 Vectors and Scalars(P44-45)IntroductionChapter 1Chapter 1Presentation of vector:On a diagram,each vector is represented by an arrow.Symbol:boldface type.(In handwrit
13、ten work,the symbol for a vector can be indicated by putting an arrow over it.IntroductionChapter 1Chapter 1Vectors follow certain vector rules of combination.Adding Vectors GraphicallyThe vector sum is the vector that extends from the tail of one vector to the head of the other vector-tail-to-tip m
14、ethod of adding vectors.(p46)3-2 Addition of Vectors(P45-46)IntroductionChapter 1Chapter 1Parallelogram Method:(P46)Is fully equivalent to the tail-to-tip method.The two vectors are drawn starting from a common origin,and a parallelogram is constructed using these two vectors as adjacent sides.Intro
15、ductionChapter 1Chapter 11 Subtracting Vectors Graphically(p46)The difference between two vectors is the vector that extends from the head of the 2nd vector to the head of the 1st vector.3-3 Subtraction of Vectors,Mulitiplication of a Vector(P46-47)IntroductionChapter 1Chapter 1 (1)The Scalar(Dot)Pr
16、oduct(点积点积):2 Multiplying a Vector by a VectorIntroductionChapter 1Chapter 1(2)The Vector(Cross)Product (叉叉叉叉积积积积)Direction is as the figure showing.IntroductionChapter 1Chapter 1 A component(分分 量量）of a vector is the projection(投投影影)of the vector on an axis.This component may be in two or three dime
17、nsional coordinate system.is is resolvedresolved to and ,to and ,oyx3-4 Components of Vectors(P47-51)IntroductionChapter 1Chapter 1 For a fixed Cartesian system,Unit vectors:Unit Vector is defined to have a magnitude(数量，数量，大小大小)exactly equal to one.In the coordinate system,Coordinate system can be chosen freely(arbitrary).unit magnitude,only indicate directions3-5 Unit Vectors(P51)IntroductionChapter 1Chapter 1P69:11IntroductionChapter 1Chapter 1Summary for Chapter OneSee P12 and P67(vector)