Equilibrium物体相对惯性参考系(如地面)静止或作匀速直线运动。Thebodyisinequilibriumifitremainsatrestormoveswithaconstantspeedinastraightlinerelativetotheinertialreferenceframe.第一章静力学公理和物体的受力分析Chapter1AxiomsofStaticsandFree-bodyDiagram§1-1静力学公理Section1.1AxiomsofStatics公理1力的平行四边形法则Axiom1Theparallelogramlaw作用在物体上同一点的两个力,可以合成为一个合力Twoforcesactingonthesamepointofabodycanbereplacedbyaresultantforce合力的作用点也在该点,合力的大小和方向,由这两个力为边构成的平行四边形的对角线确定,如图所示。.Theresultantforcecanbeobtainedbyconstructingaparallelogram,usingthetwoforcesastwoadjacentsidesoftheparallelogram.Thediagonalthatpassesthroughthepointofapplicationoftwoforcesrepresentsthemagnitudeanddirectionoftheresultantforce.合力(合力的大小与方向)(矢量的和)Resultantforce(themagnitudeanddirectionoftheresultantforce)(thevectorsum)亦可用力三角形求得合力矢Resultantforcealsocanbedeterminedbyforcetrianglerule.
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