Physics 111 Honors Classical MechanicsProf. Haimin [email protected]://solar.njit.edu/~haiminMy Research:Solar PhysicsInstrumentationMagnetic Fields and Solar ActivityWeek 1Chapter 1 Sections 1–6– Measurement– International System of Units (SI System)– Conversion of Units– Length– Time–MassMeasurements Use 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 systemSI UnitsmolmoleAmount of substancecdcandelaLuminous intensityKkelvinThermodynamic temperatureAampereElectric currentssecondTimekgkilogramMassmmeterLengthWhy should we care about SI units? Mars Climate Orbiter: http://mars.jpl.nasa.gov/msp98/orbiterhhecto2keVkkilo3MeVMmega6GeVGgiga9Ttera12Ppeta15Eexax=18dadeca1SymbolPrefix10xPrefixes for SI Unitsfmffemto−15Pmppico−12Nmnnano−9µmµmicro−6mmmmilli−3cmccenti−2ddecix = −1aatto−18SymbolPrefix10x Prefixes for SI UnitsExample of Length1x10-15Radius of a proton5x10-11Radius of hydrogen atom1x10-4Thickness of this page9x103Height of Mt. Everest6x106Radius of Earth6x1012Distance to Pluto4x1016Distance to Nearest Star (Proxima Centauri)2x1026Distance to 1stgalaxiesLength (m)MeasurementsTime1 second is the time taken by 9,192,631,770 oscillations of the light emitted by cesium-133 atomSpeed of light c=299,792,458 m/sExample of time2x10-6Lifetime of muon9x104Length of a day3x107Length of a year5x1017Age of UniverseTime (second)MeasurementsMassStandard 1: a platinum-iridium cylinder in ParisStandard 2: Carbon-12 has 12 atomic mass units (u). 1u=1.6605402x10-27kgExample of mass9x10-31Electron2x10-27Proton7x10-10Speck of dust6x10Human Body7x107Ocean Liner7x1022Moon2x1030SunMass (kg)ObjectsUnitsLanguage is mathematicsEquationsDiagrams/visualizationQuantities have dimensionsResults have unitsConsistencyPrecisionMeasurements– 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 10-3What is the radius r of the Earth? (h = 1.70 m and t = 11.1 s
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