physics 111: elementary mechanics – lecture 1 carsten denker njit physics department center for...
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Physics 111: Elementary Mechanics – Lecture 1
Carsten Denker
NJIT Physics DepartmentCenter for Solar–Terrestrial
Research
September 5, 2005 Center for Solar-Terrestrial Research
Week 1 InformationChapter 1 Sections 1-7
Measurement Units Conversion of Units
Chapter 3 Sections 1-8 Adding and multiplying vectors Unit vectors
September 5, 2005 Center for Solar-Terrestrial Research
ObjectivesBy the end of Week 1 you should be able
to List the SI units List typical prefixes of units Convert from the English to the metric system Add/subtract two vectors Explain the commutative and associative law Distinguish between scalar and vector product Work with trigonometric functions
September 5, 2005 Center for Solar-Terrestrial Research
Measurements 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 system
September 5, 2005 Center for Solar-Terrestrial Research
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.jpl.nasa.gov/msp98/orbiterhttp://mars.jpl.nasa.gov/msp98/orbiter
September 5, 2005 Center for Solar-Terrestrial Research
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
September 5, 2005 Center for Solar-Terrestrial Research
10x Prefix Symbol x=-1
deci d
-2 centi c cm -3 milli m mm -6 micro µ µA -9 nano n nm -12 pico p pm -15 femto f fm -18 atto a
Prefixes for SI Units
September 5, 2005 Center for Solar-Terrestrial Research
UnitsLanguage is mathematicsEquationsDiagrams/VisualizationQuantities have dimensionsResults have unitsConsistency
September 5, 2005 Center for Solar-Terrestrial Research
Precision Measurements
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
September 5, 2005 Center for Solar-Terrestrial Research
Vectors AB displacement from A
to B BC displacement from B
to C AC displacement from A
to C or sum or resultant of displacements AB and BC
Quantities that add like this are vectors
Vectors have magnitude and direction
September 5, 2005 Center for Solar-Terrestrial Research
Adding Vector Geometrically
Commutative Law
Associative Law
Subtraction
a b b a
d a b a b
a b c a b c
September 5, 2005 Center for Solar-Terrestrial Research
Trigonometric Functions
Please bring calculator to lecture and recitation!
September 5, 2005 Center for Solar-Terrestrial Research
Adding Vectors by Components
Components
Magnitude and Angle
cos and sinx ya a a a
2 2 and tan yx y
x
aa a a
a
September 5, 2005 Center for Solar-Terrestrial Research
Multiplying VectorsScalar Product
Vector Product
cosa b ab
and sina b c c ab
September 5, 2005 Center for Solar-Terrestrial Research
Questions
How much would a cup of coffee cost at the Cafeteria in (a) Italian Lira and (b) in Euros?
How old are you in seconds?How long is your way to school in
light-years?How would the introduction of the
metric system affect business and daily life in the US?