Physics 111, Fall 2005 Classical Mechanics

Prof. Haimin Wang

haimin@flare.njit.edu

http://solar.njit.edu/~haimin

My Research:

Solar Physics

Instrumentation

Magnetic Fields and Solar Activity

Week 1

Chapter 1 Sections 1–7– Measurement– International System of Units (SI System)– Conversion of Units– Length– Time– Mass

MeasurementsUse laws of physics to describe many different physical

systems– Small set of simple laws

– Common language is mathematics

Test laws by experiments– Select smallest set of standards and derive other standards

– International Bureau of Weights and Measures (Paris), National Bureau of Standards, etc.

– Système Internationale (SI), International System of Units, metric system, or mksA system

SI UnitsLength meter m

Mass kilogram kg

Time second s

Electric current ampere A

Thermodynamic temperature kelvin K

Luminous intensity candela cd

Amount of substance mole mol

10x Prefix Symbol x=18 exa E 15 peta P 12 tera T 9 giga G GeV 6 mega M MeV 3 kilo k keV

2 hecto h 1 deca da

Prefixes for SI Units

10x Prefix Symbol x = 1 deci d 2 centi c cm 3 milli m mm 6 micro µ µm 9 nano n Nm 12 pico p Pm

15 femto f fm 18 atto a

Prefixes for SI Units

Example of LengthMeasurements Length (m)

Distance to 1st galaxies 2x1026

Distance to Nearest Star (Proxima Centauri)

4x1016

Distance to Pluto 6x1012

Radius of Earth 6x106

Height of Mt. Everest 9x103

Thickness of this page 1x10-4

Radius of hydrogen atom 5x10-11

Radius of a proton 1x10-15

Time

1 second is the time taken by 9,192,631,770 oscillations of the light emitted by cesium-133 atom

Speed of light c=299,792,458 m/s

Example of timeMeasurements Time (second)

Age of Universe 5x1017

Length of a year 3x107

Length of a day 9x104

Lifetime of muon 2x10-6

Mass

Standard 1: a platinum-iridium cylinder in ParisStandard 2: Carbon-12 has 12 atomic mass units

(u). 1u=1.6605402x10-27 kg

Example of massObjects Mass (kg)

Sun 2x1030

Moon 7x1022

Ocean Liner 7x107

Human Body 6x10

Speck of dust 7x10-10

Proton 2x10-27

Electron 9x10-31

Units

Language is mathematicsEquationsDiagrams/visualizationQuantities have dimensionsResults have unitsConsistency

PrecisionMeasurements

– Uncertainties• Absolute• Percent

– Calculation• Result can not be better than data• Use scientific notation to show significant figures

– Examples• 3.14 + 0.5 = 3.6• 123,400,000 = 1.234 x 108

• 0.003 = 3 x 10-3

Sample Problem 1-4, p6

Chapter 3: VectorsVectors and ScalarsAdding Vectors GeometricallyComponents of VectorsUnit VectorsAdding Vectors by ComponentsVectors and the Laws of PhysicsMultiplying Vectors

– Scalar Product– Vector or Cross Product

Vectors and Scalars

Displacement Path independence

Laws of Vector Addition

Components of Vectors

Unit Vectors and Coordinate Systems

Vector Multiplication

Scalar product Vector/cross product

Sample Problem 3-4