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Physics 111 Honors Classical Mechanics
Prof. Haimin Wang
http://solar.njit.edu/~haimin
My Research:
Solar Physics
Instrumentation
Magnetic Fields and Solar Activity
Week 1
Chapter 1 Sections 1–6– 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
Why should we care about SI units? Mars Climate Orbiter: http://mars.http://mars.jpljpl..nasanasa..govgov/msp98/orbiter/msp98/orbiter
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
What is the radius r of the Earth? (h = 1.70 m and t = 11.1 s )
