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Unformatted text preview: Chapter 2: Motion in one Dimension In mechanics, three basic quantities are used Length with SI unit m Mass with SI unit kg Time with SI unit s Introduction to units International System of Units (SI Units) In mechanics, three basic quantities are used Length with SI unit m Mass with SI unit kg Time with SI unit s Will also use derived quantities These are other quantities can be expressed in terms of these Introduction to units International System of Units (SI Units) Conversion of Units When units are not consistent, you may need to convert to appropriate ones Units can be treated like algebraic quantities that can cancel each other out See the inside of the front cover of your text book for an extensive list of conversion factors Prefixes Prefixes correspond to powers of 10 The prefixes can be used with any base units They are multipliers of the base unit Examples: 1 mm = 103 m 1 mg = 103 g Conversion Always include units for every quantity, you can carry the units through the entire calculation Multiply original value by a ratio equal to one Example cm 1 . 38 in 1 cm 54 . 2 in . 15 cm ? in . 15 Simple conversion technique: carry through the units themselves in the mathematical operation Example 2: Convert the Earths escape velocity 7 mi/s to km/h Solution: 1 mile = 1.609344 km i.e. 1.609344 km/mi Similarly, there are 1/3600 (= 2.7778 104 ) h/s Therefore, 7mi / s = (7mi)(1.609344 km/mi) / s (2.7778 104 h/s ) = 40,000 km/h Simple conversion technique: carry through the units themselves in the mathematical operation Example 2: Convert the Earths escape velocity 7 mi/s to SI units Solution: 1 mile = 1609.344 m i.e. 1609.344 m/mile Therefore, 7mi / s = (7mi)(1609.344 m/mi) / s = 11,265 m/s Chapter 2 One Dimensional motion (kinematics) Example of 1D motion? Displacement Defined as the change in position during some time interval Represented as x x = x f x i SI units are meters (m) x can be positive or negative Different than distance the length of a path followed by a particle Displacement Vectors and Scalars Vector quantities need both magnitude (size or numerical value) and direction to completely describe them Will use + and signs to indicate vector directions Scalar quantities are completely described by magnitude only Vectors and Scalars Average Velocity The average velocity is rate at which the displacement occurs The SI units are m/s Is also the slope of the line in the position (distance) time graph f i average x x x v t t Average Speed Speed is a scalar quantity same units as velocity total distance / total time The average speed is not (necessarily) the magnitude of the average velocity Instantaneous Velocity The limit of the average velocity as the time interval becomes infinitesimally...
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This note was uploaded on 10/21/2010 for the course PHY 2048 taught by Professor Bose during the Spring '08 term at University of Central Florida.
 Spring '08
 bose
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