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

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

Basic Units Basic Units length (meters, m) time (sec, s) mass (kilogram, kg) (not weight)

Time 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

Mass kilogram (kg) The mass of a standard object (relic) SI system of Units: : http://physics.nist.gov/cuu/Units/backgroun d.html http://physics.nist.gov/cuu/Units/backgroun d.html

Length 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 prefixes 10 12 =1 000 000 000 000 tera (T) 10 9 =1 000 000 000 giga (G) 10 6 =1 000 000 mega (M) 10 3 = 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 Notation

scientific notation 38500 = 3.85 x10 4 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 notation 3.85 x10 4 = 38500 8.67x10 -3 = 0.00867 4.58 x10 6 = ? 6.7 x10 -4 = ? 8 x10 8 = ? 2.56 x10 -1 = ? 1.2 x10 -6 =

Significant Figures

How accurately are measurements made? 10 cm 1324 13.76cm - 10.00cm = 3.76 cm

Significant Figures How accurately are measurements made? 10 cm 1324 _____cm - _____ cm = _____ cm

Significant Figures How accurately are measurements made? time= 2.176 s 2.176 ms

Significant 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 m s

Significant 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 m s

Significant Figures How accurately are calculations made? For addition or subtraction keep # of SF in least Significant value. Round off before Calcs. X 1 = 23.4 m X 2 = 1.467 m X 3 = 123.0 m 23.4 m 1.5 m + 123.0 m 147.9 m

Dimensional Analysis

Dimensional analysis Is an equation reasonable (Is it wrong) L = L or L 3 = L 3 L/S = L/S If a =12.0 m/s 2, t = 3.0s, and d is distance Which are incorrect?

Dimensional analysis If a =12.0 m/s 2, t = 3.0s, and d is distance Which are incorrect? d =a t

Dimensional analysis If a =12.0 m/s 2, t = 3.0s, and d is distance Which are incorrect? d =a t = L T L = L T T ? Not Correct!

Dimensional analysis If a =12.0 m/s 2, t = 3.0s, and d is distance Which are incorrect? d =a t 2

Dimensional analysis If a =12.0 m/s 2, t = 3.0s, and d is distance Which are incorrect? d = =L L = L T ? Possibly! a t 2 d =1/2 a t 2 is correct!

Unit Conversions

Conversion of Units How many yards are in 45 ft? 45 ft = 15 yd 1 yd = 3 ft

Conversion 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 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 Units How many centimeters are in 2.50 kilometer? 2.50 km

Conversion of Units How many centimeters are in 2.50 kilometer? 2.50 km 1000m 1.00 km

Conversion of Units How many centimeters are in 2.50 kilometer? 2.50 km 1000m 1.00 km 100 cm 1.00m = 2.50x10 5 cm

Conversion of Units How many cm 3 are in 300 in 3 kilometer? 300 in3

Conversion of Units How many cm 3 are in 300 in 3 ? 300 in 3 (1.00 in) 3 (2.54 cm) 3

Conversion of Units How many cm 3 are in 300.0 in 3 kilometer? 300.0 in 3 1.00 in 3 16.39 cm 3 = 4916 cm 3

Conversion of Units Convert 60 mi/hr to ft/s. 60 mi hr

Conversion of Units Convert 60 mi/hr to ft/s. 60 mi hr 5280 ft 1 hr 3600 s 1.00 mi

Conversion of Units Convert 60 mi/hr to ft/s. 60 mi hr 5280 ft 1 hr 3600 s 1.00 mi =88 ft/s

Conversion 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 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 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 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 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

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