Metrics and MeasureMent Our first test will be in 5.
SI (Systeme Internationale) System of unitsFundamental unitsA quantity that cannot be measured in asimpler form Quantity Unit Distance Meter Mass Kilogram Time Seconds
Units are standardized and regulated by twoorganizations: International Bureau of Weights andMeasures (France) National Institute of Science and Technology (Maryland)All measurement tools are calibrated using thestandards stored at these locations
Standard Unit Definitions• Meter 1790 – 1/10,000,000 the distance from the north pole to the equator, measured along a line passing through Lyons, France 1875 – The distance between two lines engraved on a platinum- iridium bar stored in Paris 1984 – the distance traveled by light in a vacuum during a time interval of 1/299,792,458 s
Standard Unit Definitions• Second old – 1/86,400 of the mean solar day new – the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium atom (the vibration of the cesium atom in an atomic clock)
Standard Unit Definitions• Kilogram 1790 – mass of exactly one cubic decimeter of water 1899 – mass of the international prototype of the kilogram This apple sized piece of platinum- iridium protected behind glass in Paris is the definition of a kilogram. Because of contaminants and cleaning, the mass does change ever so slightly.
This is the future standard of the kilogram. The kilogram will soon be defined as a specific number of silicon atoms since atoms have a set mass that does not change due to cleaning, etc.The Avogadro Project has created a grapefruit sized silicon ball whichis the most perfectly spherical object ever created by man. Cost:$700,000They are in the process of COUNTING HOW MANY ATOMS ITIS COMPOSED OF!Avogadro’s number may even eventually change due to thisexperiment.
Derived unit – a unit that is composed ofother unitsExample: Newton, watt, voltA Newton is a kg m/s2
Metric PrefixesPrefix (symbol) Conversion Factor ExampleMega- (M) 106 1 MW = 106 Wkilo- (k) 103 1 kg = 103g = 1000 gcenti- (c) 10-2 1 cm = 10-2 m = 0.01 mmilli- (m) 10-3 1 mL = 10-3 L = 0.001 Lmicro- (µ) 10-6 1 m s = 10-6 s = 0.000001 s
A desk was measured to be62.52 cm tall. How manymillimeters tall is this desk?The worlds largest strawberrywas measured to be 231 g. Howmany kilograms is this?
Factor Label ConvertingWhen we convert units that are not metric systembased (ex: feet, inches, miles, etc) we have to useconversion factors. 1 mile (mi) = 1609 m 1 inch (in.) = 2.54 cm 2.2 pound (lb) = 1 kg 1 lb = 454 g 1 mL = 1 cm3 1 gallon (gal) = 3.785 L 1 gal = 8 pints
When factor label converting, we make fractions(ratios) out of the conversion factors so that theoriginal unit cancels out and the new unit remains:Example:According to the Guinness Book of World Records(2008), a man from London balanced a 352 lb car (aMini) on his head for 33 seconds. What is the massof this car in kilograms?160 kg
Usain Bolt ran the 100-m race at theBeijing Olympics in a world recordtime of 9.69 seconds. His averagespeed was 10.3 m/s.How fast was he running in miles perhour?23 mi/hr
The speed of sound is 330 m/s. Howfast is this in miles/hour?
An acre, which is 43,560 ft2, is anarea unit often used to describe thesize of a farm. What is the size of a600 acre farm in square miles?
Factor Labeling1)When a woman turns 100 years old, how any seconds has she lived?2)If one Deutschmark (the West German unit of currency) is worth 40 cents and gasoline costs1.30 Deustchmarks per liter, what is its cost in dollars per gallon?3)The gasoline consumption of a small car is 17 km/l. How many miles per gallon is this?4)The speed limit on a highway in Lower Slobbovia was given as 150,000 furlongs per fortnight.How many miles per hour is this? (One furlong is 1/8 mile and a fortnight is 14 days. A furlongoriginally referred to the length of a plowed furrow.)5)A speed limit sign on a Canadian road reads “80 km/h.” What is this limit in miles per hour?7)An acre, which is 43,560 ft2, is an area unit often used to describe the size of a farm. What is thesize of a 600 acre farm in square miles?8)A football field is 120 yd long by 53 yd wide. What is the size of a football field in acres?
The GoogolPhysicists, mathematicians and othersoften deal with very large numbers.The number 10100 has been given thename googol by mathematicians. Let’scompare some large numbers in physicsto the googol.
Approximately now many atoms make upthe earth? For simplicity, take the averageatomic mass of the atoms to be 14 g/mole.Mass of Earth = 6 x 1024 kg 2.58 x 1050 atoms
Approximately how many neutrons arein a neutron star? Neutron stars aremade up of neutrons and haveapproximately twice the mass of the sun.Mass of sun = 1.99 x 1030 kgMass of neutron = 1.675 x 10-27 kg 2.38 x 1057 neutrons
In one theory of the origin of the universe, theuniverse at a very early time had a density (massdivided by volume) of 1015 g/cm3, while it radiuswas approximately the present distance of theearth ot the sun. Assuming 1/3 of the particleswere protons, 1/3 were neutrons and theremaining 1/3 were electrons, how many particlesmade up the universe?Distance of earth to sun = 1.49 x1011 mMass of proton = 1.673 x 10-27 kgMass of electron = 9.11 x 10-31 kg 4.12 x 1078 particles
Googol fun facts:A googolplex is a 1 followed by a googol ofzeroes.The word googol was invented in 1938 by the nineyear old nephew of mathematician Edward Kasner.The name of the website Google is a misspelling ofthe word.Q: Who shops at the Googolplex Mall?A: Phineas and Ferb