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1、Chapter 1 Essential Concepts and Statics Review力為兩種物體間的一種“交互作用”何謂力(Force)?作用力:施力物對受力物之力反作用力:受力物反作用於施力物之力1External Forces 外力是從元件外部作用於元件的力與力矩 Reactive Forces(Reactions)作用於元件支撐點（Supports）或連結點（Connections）的外力特稱為反應力Applied force(Loading)其它的外力稱為負荷（Loading）Internal force於物體內部維持其結合的力與力矩稱為內力外力、反應力、負荷與內力：外力、反
2、應力、負荷與內力：2例子LoadingLoadingReactionReactionReaction3自由體圖（自由體圖（Free Body Diagram）將元件中所關心的部份獨立割出，以方便表示靜力平衡，此圖示稱為自由體圖。若自由體圖分割元件之接觸面，則此面上將有外力作用。Free body diagram4Free body diagram若自由體圖將元件切割，則在切割面上有內力作用。為彎矩。為作用於斷面的內力52.元件上任一點之合力矩為零靜力平衡一元件在靜力平衡時：1.外力之合力為零6The rigid structure shown in the left figure is sub
3、jected to a 5000-lb force P.The connections at joints A,B,and C are frictionless pins.Determine the forces at A and B on member AB.算例7解8算例A 900-kg mss is supported by a roller that can move along a beam,as shown in the left figure.The beam is supported by a pin at A and a roller at B.(a)Neglect the
4、mass of the beam and determine the reactions at A and B.(b)If the mass of the beam is 8.5 kg/m,determine the reactions at A and B.9解(a)(b)10Internal forceFor the arbitrary body,F1,F2,F3,F4,and F5 are external forces.R:resultant forceC:resultant couple11直角坐標上之內力的標示(P)12算例A post and bracket are used t
5、o support a pulley,as shown in Fig.1-19a.A cable passing over the pulley supports a 2200-N force.Determine the internal forces on a section at the support at A.13解14The cantilever beam shown in Fig.1-20a is subject to both concentrated and distributed loads.Determine(a)the support reactions and(b)the internal forces on a section 4 m to the right of the support at A.算例15(a)16(b)171819