1. What is physics?Physics is a way of describing the physicalworld 6th Century B.C. in the Greek city ofMiletus (now in Turkey) a group of mencalled physikoi tried to answer questionsabout the natural world. Physics comesfrom the Greek word physismeaning nature, and the Latin wordphysica meaning natural things.

2. Investigations in physics generally followthe scientific method 3. Units in PhysicsSome old measuring units 4. Physics experiments involve themeasurement of a variety ofquantities. These measurements should beaccurate. The first step in ensuring accuracy isdefining the units in which themeasurements are made. 5. The Nature of MeasurementA Measurement is a quantitativeobservation consisting of TWO partsPart 1 numberPart 2 - scale (unit)Examples:20 grams6.63 x 10-34 Joules 6. The Fundamental SI Units(le Systme International, SI)Physical Quantity (symbol) Name AbbreviationmKgSAKMolcd 7. SI Definitionsmeter:The meter is the length of the pathtravelled by light in vacuum during a timeinterval of 1/299 792 458 of a second.Historical InternationalPrototype Metre bar, madeof an alloy of platinum andiridium, that was thestandard from 1889 to1960, then this wasreplaced by the above-mentioneddefinition. 8. SI Definitionskilogram:The kilogram isthe unit of mass; it isequal to the mass ofthe internationalprototype of thekilogram. This is madeof platinum-iridium & itis kept at the BIPM, inFrance.Photograph @ BIPMVisit the page 9. SI Definitionssecond:The unit of time, it was definedoriginally as the fraction 1/86 400 of themean solar day.In 1967 it was replaced by the followingdefinition :The second is the duration of9 192 631 770 periods of the radiationcorresponding to the transition between thetwo hyperfine levels of the ground state ofthe cesium 133 atom. 10. SI Definitionsampere:The ampere is that constant currentwhich, if maintained in two straight parallelconductors of infinite length, of negligiblecircular cross-section, and placed 1 meterapart in vacuum, would produce betweenthese conductors a force equal to 2 x 10-7newton per meter of length. 11. SI Definitionscandela:The candela is the luminousintensity, in a given direction, ofa source that emitsmonochromatic radiation offrequency 540 x 1012 hertz andthat has a radiant intensity inthat direction of 1/683 watt persteradian(http://en.wikipedia.org/wiki/Steradian) 12. SI Definitionskelvin:The kelvin, unit of thermodynamictemperature, is the fraction 1/273.16 ofthe thermodynamic temperature of thetriple point of water.mole:The mole is the amount of substanceof a system which contains as manyelementary entities as there are atoms in0.012 kilogram of carbon 12. 13. Derived unitsDerived units are combinations of fundamentalunits.Examples:speed (v) = distance/timeunits: m/sacceleration (a) = velocity / timeunits: m/s/s = m/s2force (F) = mass x accelerationunits: kgm/s2 = N (Newton)energy (E) = force x distanceunits: kgm2/s2 = Nm = J (Joule)charge (Q) = current x timeunits: As = C (Coulomb) 14. SI Derived Units 15. SI PrefixesCommon to ChemistryPrefix Unit Abbr. ExponentKilo k 103Deci d 10-1Centi c 10-2Milli m 10-3Micro 10-6 16. Metric Conversionsgm103 102 101 L 10-1 10-2 10-3kilo hecto deka deci centi milliBaseunitConversions in the metric system aremerely a matter of moving a decimal point.The base unit means the you have aquantity (grams, meters, Liters, etc withouta prefix. 17. Metric Conversionsgm103 102 101 L 10-1 10-2 10-3kilo hecto deka deci centi milliBaseunit18 L1 2 318 liters = 18 000 millilitersExample #1: Convert 18 liters to milliliters 18. Metric Conversionsgm103 102 101 L 10-1 10-2 10-3kilo hecto deka deci centi milliBaseunit3 2 1450 mg = 0.450 g 450 mgExample #2: Convert 450 milligrams to grams 19. Metric Conversionsgm103 102 101 L 10-1 10-2 10-3kilo hecto deka deci centi milliBaseunit20 kg1 2 3 4 5 620 kg = 20 000 000 mgExample #3: Convert 20 kilograms to milligrams