Metric systemMetric system
Dr. Robert M. MacKay
Clark College PhysicsClark College
Basic UnitsBasic Units
length (meters, m) time (sec, s) mass (kilogram, kg) (not weight)
TimeTime
time (sec, s) 1/86 400 of a mean solar day 1 sec is the time required for 9, 192, 631, 770
oscillations of Cs-133 atom (1967)
www.time.gov
MassMass
kilogram (kg) The mass of a standard object (relic)
SI system of Units: : http://physics.nist.gov/cuu/Units/background.html
LengthLength 1.0 meter (1/10 000 000 of distance from pole
to equator) distance light travels in 1/299 792 458 s (1983) 1 m =39.37 inches 1.0 inch = 2.54000000
cm 1 m = 100 cm (centi-meter) = 1000 mm (milli-meter) = 1 000 000 µm (micro-meter) = 1 000 000 000 nm (nano-meter) = 0.001 km (kilo-meter)
metric prefixesmetric prefixes 1012 =1 000 000 000 000 tera (T) 109 =1 000 000 000 giga (G) 106 =1 000 000 mega (M) 103 = 1 000 kilo (k) 10-2= 0.01 centi (c) 10-3= 0.001 milli (m) 10-6 = 0.000 001 micro (µ) 10-9= 0.000 000 001 nano (n) 10-12=0.000 000 000 001 pico (p)
Scientific NotationScientific Notation
scientific notationscientific notation
38500 = 3.85 x104
0.00867 = 8.67x10-3
458 = 4.58 x10?
6700000 = 6.7 x10?
80000 = 8 x10?
0.00256 = 2.56 x10?
0.00000012= 1.2 x10?
scientific notationscientific notation 3.85 x104 = 38500 8.67x10-3 = 0.00867 4.58 x10
6 = ?
6.7 x10-4
= ?
8 x108 = ?
2.56 x10-1
= ?
1.2 x10-6
=
Significant FiguresSignificant Figures
Significant FiguresSignificant Figures
How accurately are measurements made?
10cm 1 32 4
13.76cm - 10.00cm = 3.76 cm
Significant FiguresSignificant Figures
How accurately are measurements made?
10cm 1 32 4
_____cm - _____ cm = _____ cm
Significant FiguresSignificant Figures
How accurately are measurements made?
time= 2.176 s
2.176ms
Significant FiguresSignificant Figures
How accurately are calculations made?
V=5.67 m/s t= 3.279 s
D=V t = ?
= 5.67 3.279 s
= 18.6 m
ms
Significant FiguresSignificant Figures How accurately are calculations made? For Multiplication or Division keep # of SF in least Significant value. Round off
After Calcs.
V=5.67 m/s t= 3.279 s
D=V t = ?
= 5.67 3.279 s
= 18.6 m
ms
Significant FiguresSignificant Figures How accurately are calculations made? For addition or subtraction keep # of SF in least Significant value. Round off
before Calcs.
X1 = 23.4 m
X2 = 1.467 m
X3 = 123.0 m
23.4 m
1.5 m
+ 123.0 m
147.9 m
Dimensional AnalysisDimensional Analysis
Dimensional analysisDimensional analysis Is an equation reasonable (Is it wrong) L = L or L3 = L3 L/S = L/S
If a =12.0 m/s2 , t = 3.0s, and d is distance Which are incorrect?
Dimensional analysisDimensional analysis If a =12.0 m/s2 , t = 3.0s, and d is distance Which are incorrect?
d = a t
Dimensional analysisDimensional analysis If a =12.0 m/s2 , t = 3.0s, and d is distance Which are incorrect?
d = a t
= L
TL = L
T TT
? Not Correct!
Dimensional analysisDimensional analysis If a =12.0 m/s2 , t = 3.0s, and d is distance Which are incorrect?
d = a t2
Dimensional analysisDimensional analysis If a =12.0 m/s2 , t = 3.0s, and d is distance Which are incorrect?
d =
= LL = L
T TT T
? Possibly!
a t2
d = 1/2 a t2 is correct!
Unit ConversionsUnit Conversions
Conversion of UnitsConversion of Units
How many yards are in 45 ft? 45 ft = 15 yd
1 yd = 3 ft
Conversion of UnitsConversion of Units
How many yards are in 45 ft? 45 ft = 15 yd
1 yd = 3 ft
1 yd 45 ft 3 ft
= 15 yd
Conversion of UnitsConversion of Units How many centimeters are in 2.50 kilometer? Write down known value draw a line to separate numerator from denominator use a unit factor conversion to go from one unit to next use unit analysis to keep track of units
Conversion of UnitsConversion of Units
How many centimeters are in 2.50 kilometer?
2.50 km
Conversion of UnitsConversion of Units
How many centimeters are in 2.50 kilometer?
2.50 km1000m
1.00 km
Conversion of UnitsConversion of Units
How many centimeters are in 2.50 kilometer?
2.50 km1000m
1.00 km
100 cm
1.00m= 2.50x105 cm
Conversion of UnitsConversion of Units
How many cm3 are in 300 in3 kilometer?
300 in3
Conversion of UnitsConversion of Units
How many cm3 are in 300 in3?
300 in3
(1.00 in)3
(2.54 cm)3
Conversion of UnitsConversion of Units
How many cm3 are in 300.0 in3 kilometer?
300.0 in3
1.00 in3
16.39 cm3
= 4916 cm3
Conversion of UnitsConversion of Units
Convert 60 mi/hr to ft/s.
60 mihr
Conversion of UnitsConversion of Units
Convert 60 mi/hr to ft/s.
60 mihr
5280 ft 1 hr
3600 s1.00 mi
Conversion of UnitsConversion of Units
Convert 60 mi/hr to ft/s.
60 mihr
5280 ft 1 hr
3600 s1.00 mi= 88 ft/s
Conversion FunConversion Fun
Ratio of an igloo's circumference to its diameter = Eskimo Pi
2000 pounds of Chinese soup = Won ton
1 millionth of a mouthwash = 1 microscope
Conversion FunConversion Fun Time it takes to sail 220 yards at 1 nautical mile
per hour =Knot-furlong
365.25 days of drinking low-calorie beer because it's less filling = 1lite year
16.5 feet in the Twilight Zone = 1 Rod Serling
Conversion FunConversion Fun 1,000,000 aches = 1 megahertz
Weight an evangelist carries with God = 1 billigram
Basic unit of laryngitis = 1 hoarsepower
Shortest distance between two jokes = A straight line
Conversion FunConversion Fun 453.6 graham crackers = 1 pound cake 1 million microphones = 1 megaphone 1 million bicycles = 2 megacycles 365.25 days = 1 unicycle 2000 mockingbirds = two kilomockingbirds
Conversion FunConversion Fun
10 rations = 1 decoration 10 millipedes = 1 centipede 3 1/3 tridents = 1 decadent 10 monologs = 5 dialogs 5 dialogs = 1 decalog 2 monograms = 1 diagram 8 nickels = 2 paradigms 2 wharves = 1 paradox 100 Senators = Not 1 decision