Standards of Quantities n agreedin1960by an international committee SI – Systéme International n n main system used in this textbook

Length Standard Meter n n Units nThe SI unit is meter (m)اﻟﻣﺗر ھﻲ لﻮﻃاﻟ وﺣدة The meter is defined as the distance traveled by light in a vacuum a time of 1/299 792 458 second nﻣﻘداره زﻣن ﻓﻲ اﻟﺿوء ﯾﻘطﻌﮭﺎ اﻟﺗﻲ اﻟﻣﺳﺎﻓﺔ اﻧﮫ ىلﻋ اﻟﻣﺗر ف4587921/299ﺛﺎﻧﯾﺔ Page 4

See Table 1.1 for some examples of lengths

Mass n n n n Units The SI unit is kilogram (kg)اﻟﻛﯾﻠوﻏرام ھﻲ اﻟﻛﺗﻠﺔ وﺣدة The kilogram is defined as the mass of a specific platinum–iridium alloy cylinder kept at the International Bureau of Weights and Measures at Sèvres, France ارﯾدﯾوم-ﻣنﺳﺑﯾﻛﺔاﻟﺑﻼﺗﯾﻧﯾوم اﻧﮫﻣﺻﻧوﻋﺔﻮﻃﻛﺗﻠﺔاﺳ :اﻧﮫىلﻋ اﻟﻛﯾﻠوﻏرام ﯾﻌرف ﺑﻔرﻧﺳﺎ ﺳﯾﻔري ﻓﻲ اﻟﻣﻘﺎﯾﯾس و ﻟﻸوزان اﻟدوﻟﻲ اﻟﻣﻛﺗب ﻓﻲ ﻣﺣﻔوظﺔ Table 1.2 for masses of various objects Standard Kilogram Page 4

Time n n n The SIunit is seconds, s nاﻟﺛﺎﻧﯾﺔ ھﻲ اﻟزﻣن وﺣدة The second is defined as 9 192 631 770 times the period of vibration of radiation from the cesium- 133 atom nاﻧﮭﺎ ىلﻋ اﻟﺛﺎﻧﯾﺔ ﻧﻌرف7706311929اﻟﻼزم اﻟزﻣن ﺿﻌف -اﻟﺳﯾزﯾوم ذرة ﻣن اﻟﺻﺎدر ﻟﻼﺷﻌﺎع133 See Table 1.3 for some approximate time intervals A cesium fountain atomic clock. The clock will neither gain nor lose a second in 20 million years. Page 5

Prefixes n n n n n n + Q: The thickness of a micron, is a. 10 m b. 10 m c. 10 m d. 10 m -3 -9 -6 -12 Prefixes correspond to powers of 10 Each prefix has a specific name Each prefix has a specific abbreviation The prefixes can be used with any base units They are multipliers of the base unit Examples: n1 mm = 10 m n1 mg = 10 g n1 nm = 10 m -3 -3 -9 Small unit big unit - big unit small unit X 1 0 X1 0 Page 6

Basic Quantities and Their Dimension n The word dimension denotes the physical nature of a quantity Dimensions are denoted with square brackets []ﻣرﺑﻌﺗﯾن ﺑﺣﺎﺻرﺗﯾن ﻋﻧﮭﺎ ﯾﻌﺑر اﻻﺑﻌﺎد n اﻟﻔﯾز ﻟﻠﻛﻣﯾﺎت اﻟﻔﯾزﯾﺎﺋﯾﺔ اﻟطﺑﯾﻌﺔ ﻋن ﺗﻌﺑر اﻟﺑﻌد ﻛﻠﻣﺔ n n n n Length [L] Mass [M] Time [T] [L] [M] [T] لﻮﻃاﻟ اﻟﻛﺗﻠﺔ اﻟزﻣن Page 7&8

Dimensional Analysis اﻟﺑﻌدي اﻟﺗﺣﻠﯾل n n n n n n n Technique to check the correctness of an equation or to assist in deriving an equat ﻣﻌﺎدﻟﺔ اﺷﺗﻘﺎق ﻓﻲ ﻟﻠﻣﺳﺎﻋدة أو ﻣﻌﺎدﻟﺔ ﺻﺣﺔ ﻣن ﻟﻠﺗﺣﻘق ﯾﻘﺔﺮﻃ Dimensions (length, mass, time, combinations) can be treated as algebraic quantiti nadd, subtract, multiply, divide ﺗﻘﺳ و ﺗﺿرب ح،ﺮﻃﺗ ﺗﺟﻣﻊ، ﺟﺑرﯾﺔ، ﻛﻣﯾﺎت اﻧﮭﺎ ىلﻋ ﻣﻌﮭﺎ اﻟﺗﻌﺎﻣل ﯾﻣﻛن اﻻﺑﻌﺎد Both sides of equation must have the same dimensions اﻷﺑﻌﺎد ﻧﻔس ﻟﮭم ﯾﻛون أن ﯾﺟب اﻟﻣﻌﺎدﻟﺔ ﻓﻲﺮﻃ Cannot give numerical factors: this is its limitation ﻋددﯾﺔ ﻣﻌﺎﻣﻼت ﺗﻌطﻲ أن اﻟﺑﻌدي اﻟﺗﺣﻠﯾل ﯾﻘﺔﺮﻃﻟ ﯾﻣﻛن ﻻ Page 7 &8

Dimensional Analysis, cont. n n Dimensions of some common quantities are given below أدﻧﺎه ﺑﺎﻟﺟدول ﻣﻌطﺎه اﻟﻛﻣﯾﺎت ﺑﻌض أﺑﻌﺎد Basic physical quantity Length Mass Time m t Symbol Unit m Kg s Dimension L M T l