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082-Engineering-Mathematics-Anthony-Croft-Robert-Davison-Martin-Hargreaves-James-Flint-Edisi-5-2017

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7 Vectors

Contents 7.1 Introduction 224

7.2 Vectorsandscalars:basicconcepts 224

7.3 Cartesiancomponents 232

7.4 Scalarfieldsandvectorfields 240

7.5 Thescalarproduct 241

7.6 Thevectorproduct 246

7.7 Vectorsofndimensions 253

Reviewexercises7 255

7.1 INTRODUCTION

Certainphysicalquantitiesarefullydescribedbyasinglenumber:forexample,themass

of a stone, the speed of a car. Such quantities are called scalars. On the other hand,

some quantities are not fully described until a direction is specified in addition to the

number. For example, a velocity of 30 metres per second due east is different from a

velocityof30metrespersecondduenorth.Thesequantitiesarecalledvectorsanditis

importanttodistinguishthemfromscalars.There aremany engineering applications in

which vector and scalar quantities play important roles. For example, speed, potential,

work and energy are scalar quantities, while velocity, electric and magnetic forces, the

position of a robot and the state-space representation of a system can all be described

by vectors. A variety of mathematical techniques have been developed to enable useful

calculations tobe carriedout usingvectors and inthischapter these will be discussed.

7.2 VECTORSANDSCALARS:BASICCONCEPTS

Scalarsarethesimplestquantitieswithwhichtodeal;thespecificationofasinglenumberisallthatisrequired.Vectorsalsohaveadirectionanditisusefultoconsideragraphical

representation. Thus the line segment AB of length 4 in Figure 7.1 can represent

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