Metric system Dr. Robert M. MacKay Clark College Physics Clark College

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